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Custom Graph Components

You can extend Rasa with custom NLU components and policies. This page provides a guide on how to develop your own custom graph components.

Rasa provides a variety of NLU components and policies out of the box. You can customize them or create your own components from scratch by using custom graph components.

To use your custom graph component with Rasa it has to fulfill the following requirements:

Graph Components

Rasa uses the passed in model configuration to build a directed acyclic graph. This graph describes the dependencies between the items in your model configuration and how data flows between them. This has two major benefits:

  • Rasa can use the computational graph to optimize the execution of your model. Examples for this are efficient caching of training steps or executing independent steps in parallel.
  • Rasa can represent different model architectures flexibly. As long as the graph remains acyclic Rasa can in theory pass any data to any graph component based on the model configuration without having to tie the underlying software architecture to the used model architecture.

When translating the model configuration to the computational graph policies and NLU components become nodes within this graph. While there is a distinction between policies and NLU components in your model configuration, the distinction is abstracted away when they are placed within the graph. At this point policies and NLU components become abstract graph components. In practice this is represented by the GraphComponent interface: Both policies and NLU components have to inherit from this interface to become compatible and executable for Rasa's graph.

Visualization of the Rasa Graph Architecture

Getting Started

Before you get started, you have to decide whether you want to implement a custom NLU component or a policy. If you are implementing a custom policy, then we recommend extending the existing rasa.core.policies.policy.Policy class which already implements the GraphComponent interface.

from rasa.core.policies.policy import Policy
from rasa.engine.recipes.default_recipe import DefaultV1Recipe
# TODO: Correctly register your graph component
@DefaultV1Recipe.register(
[DefaultV1Recipe.ComponentType.POLICY_WITHOUT_END_TO_END_SUPPORT], is_trainable=True
)
class MyPolicy(Policy):
...

If you want to implement a custom NLU component then start out with the following skeleton:

from typing import Dict, Text, Any, List
from rasa.engine.graph import GraphComponent, ExecutionContext
from rasa.engine.recipes.default_recipe import DefaultV1Recipe
from rasa.engine.storage.resource import Resource
from rasa.engine.storage.storage import ModelStorage
from rasa.shared.nlu.training_data.message import Message
from rasa.shared.nlu.training_data.training_data import TrainingData
# TODO: Correctly register your component with its type
@DefaultV1Recipe.register(
[DefaultV1Recipe.ComponentType.INTENT_CLASSIFIER], is_trainable=True
)
class CustomNLUComponent(GraphComponent):
@classmethod
def create(
cls,
config: Dict[Text, Any],
model_storage: ModelStorage,
resource: Resource,
execution_context: ExecutionContext,
) -> GraphComponent:
# TODO: Implement this
...
def train(self, training_data: TrainingData) -> Resource:
# TODO: Implement this if your component requires training
...
def process_training_data(self, training_data: TrainingData) -> TrainingData:
# TODO: Implement this if your component augments the training data with
# tokens or message features which are used by other components
# during training.
...
return training_data
def process(self, messages: List[Message]) -> List[Message]:
# TODO: This is the method which Rasa Open Source will call during inference.
...
return messages

Read the following sections to find out how to solve the TODOs in the example above and what other methods need to be implemented in your custom component.

custom tokenizers

If you create a custom tokenizer, you should extend the rasa.nlu.tokenizers.tokenizer.Tokenizer class. The train and process methods are already implemented so you only need to overwrite the tokenize method.

The GraphComponent interface

To run your custom NLU component or policy with Rasa it must implement the GraphComponent interface.

from __future__ import annotations
from abc import ABC, abstractmethod
from typing import List, Type, Dict, Text, Any, Optional
from rasa.engine.graph import ExecutionContext
from rasa.engine.storage.resource import Resource
from rasa.engine.storage.storage import ModelStorage
class GraphComponent(ABC):
"""Interface for any component which will run in a graph."""
@classmethod
def required_components(cls) -> List[Type]:
"""Components that should be included in the pipeline before this component."""
return []
@classmethod
@abstractmethod
def create(
cls,
config: Dict[Text, Any],
model_storage: ModelStorage,
resource: Resource,
execution_context: ExecutionContext,
) -> GraphComponent:
"""Creates a new `GraphComponent`.
Args:
config: This config overrides the `default_config`.
model_storage: Storage which graph components can use to persist and load
themselves.
resource: Resource locator for this component which can be used to persist
and load itself from the `model_storage`.
execution_context: Information about the current graph run.
Returns: An instantiated `GraphComponent`.
"""
...
@classmethod
def load(
cls,
config: Dict[Text, Any],
model_storage: ModelStorage,
resource: Resource,
execution_context: ExecutionContext,
**kwargs: Any,
) -> GraphComponent:
"""Creates a component using a persisted version of itself.
If not overridden this method merely calls `create`.
Args:
config: The config for this graph component. This is the default config of
the component merged with config specified by the user.
model_storage: Storage which graph components can use to persist and load
themselves.
resource: Resource locator for this component which can be used to persist
and load itself from the `model_storage`.
execution_context: Information about the current graph run.
kwargs: Output values from previous nodes might be passed in as `kwargs`.
Returns:
An instantiated, loaded `GraphComponent`.
"""
return cls.create(config, model_storage, resource, execution_context)
@staticmethod
def get_default_config() -> Dict[Text, Any]:
"""Returns the component's default config.
Default config and user config are merged by the `GraphNode` before the
config is passed to the `create` and `load` method of the component.
Returns:
The default config of the component.
"""
return {}
@staticmethod
def supported_languages() -> Optional[List[Text]]:
"""Determines which languages this component can work with.
Returns: A list of supported languages, or `None` to signify all are supported.
"""
return None
@staticmethod
def not_supported_languages() -> Optional[List[Text]]:
"""Determines which languages this component cannot work with.
Returns: A list of not supported languages, or
`None` to signify all are supported.
"""
return None
@staticmethod
def required_packages() -> List[Text]:
"""Any extra python dependencies required for this component to run."""
return []
@classmethod
def fingerprint_addon(cls, config: Dict[str, Any]) -> Optional[str]:
"""Adds additional data to the fingerprint calculation.
This is useful if a component uses external data that is not provided
by the graph.
"""
return None

create

The create method is used to instantiate your graph component during training and has to be overridden. Rasa passes the following parameters when calling the method:

  • config: This is your component's default configuration merged with the configuration provided to the graph component in the model configuration file.
  • model_storage: You can use this to persist and load your graph component. See the model persistence section for further details on its usage.
  • resource: The unique identifier of your component within the model_storage. See the model persistence section for further details on its usage.
  • execution_context: This provides additional information about the current mode of execution:
    • model_id: A unique identifier for the model used during inference. This parameter is None during training.
    • should_add_diagnostic_data: If True then additional diagnostic metadata should be added to your graph component's predictions on top of the actual prediction.
    • is_finetuning: If True then the graph component can be trained using finetuning.
    • graph_schema: The graph_schema describes the computational graph which is used to train your assistant or to make predictions with it.
    • node_name: The node_name is a unique identifier for the step in the graph schema which is fulfilled by the called graph component

load

The load method is used to instantiate your graph component during inference. The default implementation of this method calls your create method. It is recommended to override this if your graph component persists data as part of the training. See create for a description of the individual parameters.

get_default_config

The method get_default_config returns the default configuration for your graph component. Its default implementation returns an empty dictionary which implies that the graph component does not have any configuration. Rasa will update the default configuration with the given in the configuration file at runtime.

supported_languages

The method supported_languages specifies which languages a graph component supports. Rasa will use the language key in the model configuration file to validate that the graph component is valid for usage with the specified language. If a graph component returns None (this is the default implementation), it indicates that the graph component supports all languages which are not part of not_supported_languages.

Examples:

  • []: The graph component does not support any language
  • None: All languages are supported expect the languages defined in not_supported_languages
  • ["en"]: The graph component can only be used with English conversations.

not_supported_languages

The method not_supported_languages specifies which languages your graph component does not support. Rasa will use the language key in the model configuration file to validate that your graph component is valid for usage with the specified language. If your graph component returns None (this is the default implementation), you indicate that it supports all languages which are specified in supported_languages.

Examples:

  • None or []: All languages specified in supported_languages are supported.
  • ["en"]: The graph component can be used with any language except English.

required_packages

The required_packages method indicates which extra Python packages need to be installed to use this graph component. Rasa will raise an error during execution if the required libraries are not found at runtime. By default, this method returns an empty list which implies that your graph component does not have any extra dependencies.

Examples:

  • []: No extra packages are required to use this graph component
  • ["spacy"]: The Python package spacy needs to be installed to use this graph component.

Model Persistence

Some graph components require persisting data during training which should be available to the graph component at inference time. A typical use case is storing model weights. Rasa provides the model_storage and resource parameters to your graph component's create and load method for this purpose as shown in the snippet below. The model_storage provides access to data from all graph components. The resource allows you to uniquely identify your graph component's location in the model storage.

from __future__ import annotations
from typing import Any, Dict, Text
from rasa.engine.graph import GraphComponent, ExecutionContext
from rasa.engine.storage.resource import Resource
from rasa.engine.storage.storage import ModelStorage
class MyComponent(GraphComponent):
@classmethod
def create(
cls,
config: Dict[Text, Any],
model_storage: ModelStorage,
resource: Resource,
execution_context: ExecutionContext,
) -> MyComponent:
...
@classmethod
def load(
cls,
config: Dict[Text, Any],
model_storage: ModelStorage,
resource: Resource,
execution_context: ExecutionContext,
**kwargs: Any
) -> MyComponent:
...

Writing to the Model Storage

The snippet below illustrates how to write your graph component's data to the model storage. To persist your graph component after training, the train method will need to access to the values of model_storage and resource. Therefore, you should store the values of model_storage and resource at initialization time.

Your graph component's train method must return the value of resource so that Rasa can cache the training results between trainings. The self._model_storage.write_to(self._resource) context manager provides a path to a directory where you can persist any data required by your graph component.

from __future__ import annotations
import json
from typing import Optional, Dict, Any, Text
from rasa.engine.graph import GraphComponent, ExecutionContext
from rasa.engine.storage.resource import Resource
from rasa.engine.storage.storage import ModelStorage
from rasa.shared.nlu.training_data.training_data import TrainingData
class MyComponent(GraphComponent):
def __init__(
self,
model_storage: ModelStorage,
resource: Resource,
training_artifact: Optional[Dict],
) -> None:
# Store both `model_storage` and `resource` as object attributes to be able
# to utilize them at the end of the training
self._model_storage = model_storage
self._resource = resource
@classmethod
def create(
cls,
config: Dict[Text, Any],
model_storage: ModelStorage,
resource: Resource,
execution_context: ExecutionContext,
) -> MyComponent:
return cls(model_storage, resource, training_artifact=None)
def train(self, training_data: TrainingData) -> Resource:
# Train your graph component
...
# Persist your graph component
with self._model_storage.write_to(self._resource) as directory_path:
with open(directory_path / "artifact.json", "w") as file:
json.dump({"my": "training artifact"}, file)
# Return resource to make sure the training artifacts
# can be cached.
return self._resource

Reading from the Model Storage

Rasa will call the load method of your graph component to instantiate it for inference. You can use the context manager self._model_storage.read_from(resource) to get a path to the directory where your graph component's data was persisted. Using the provided path you can then load the persisted data and initialize your graph component with it. Note that the model_storage will throw a ValueError in case no persisted data was found for the given resource.

from __future__ import annotations
import json
from typing import Optional, Dict, Any, Text
from rasa.engine.graph import GraphComponent, ExecutionContext
from rasa.engine.storage.resource import Resource
from rasa.engine.storage.storage import ModelStorage
class MyComponent(GraphComponent):
def __init__(
self,
model_storage: ModelStorage,
resource: Resource,
training_artifact: Optional[Dict],
) -> None:
self._model_storage = model_storage
self._resource = resource
@classmethod
def load(
cls,
config: Dict[Text, Any],
model_storage: ModelStorage,
resource: Resource,
execution_context: ExecutionContext,
**kwargs: Any,
) -> MyComponent:
try:
with model_storage.read_from(resource) as directory_path:
with open(directory_path / "artifact.json", "r") as file:
training_artifact = json.load(file)
return cls(
model_storage, resource, training_artifact=training_artifact
)
except ValueError:
# This allows you to handle the case if there was no
# persisted data for your component
...

Registering Graph Components with the Model Configuration

To make your graph component available to Rasa you may have to register your graph component with a recipe. Rasa uses recipes to translate the content of your model configuration to executable graphs. Currently, Rasa supports the default.v1 and the experimental graph.v1 recipes. For default.v1 recipe, you need to register your graph component by using the DefaultV1Recipe.register decorator:

from rasa.engine.graph import GraphComponent
from rasa.engine.recipes.default_recipe import DefaultV1Recipe
@DefaultV1Recipe.register(
component_types=[DefaultV1Recipe.ComponentType.INTENT_CLASSIFIER],
is_trainable=True,
model_from="SpacyNLP",
)
class MyComponent(GraphComponent):
...

Rasa uses the information provided in the register decorator and the position of your graph component within the configuration file to schedule the execution of your graph component with its required data. The DefaultV1Recipe.register decorator allows you to specify the following details:

  • component_types: This specifies what purpose your graph component fulfills within the assistant. It is possible to specify multiple types (e.g. if your graph component is both intent classifier and entity extractor):

    • ComponentType.MODEL_LOADER: Component type for language models. Graph components of this type provide pretrained models to other graph components' train, process_training_data and process methods if they have specified model_from=<model loader name>. This graph component is run during training and inference. Rasa will use the graph component's provide method to retrieve the model which should be provided to dependent graph components.

    • ComponentType.MESSAGE_TOKENIZER: Component type for tokenizers. This graph component is run during training and inference. Rasa will use the graph component's train method if is_trainable=True is specified. Rasa will use process_training_data for tokenizing training data examples and process to tokenize messages during inference.

    • ComponentType.MESSAGE_FEATURIZER: Component type for featurizers. This graph component is run during training and inference. Rasa will use the graph component's train method if is_trainable=True is specified. Rasa will use process_training_data for featurizing training data examples and process to featurize messages during inference.

    • ComponentType.INTENT_CLASSIFIER: Component type for intent classifiers. This graph component is run only during training if is_trainable=True. The graph component is always run during inference. Rasa will use the graph component's train method if is_trainable=True is specified. Rasa will use the graph component's process method to classify the intent of messages during inference.

    • ComponentType.ENTITY_EXTRACTOR: Component type for entity extractors. This graph component is run only during training if is_trainable=True. The graph component is always run during inference. Rasa will use the graph component's train method if is_trainable=True is specified. Rasa will use the graph component's process method to extract entities during inference.

    • ComponentType.POLICY_WITHOUT_END_TO_END_SUPPORT: Component type for policies which don't require additional end-to-end features (see end-to-end training for more information). This graph component is run only during training if is_trainable=True. The graph component is always run during inference. Rasa will use the graph component's train method if is_trainable=True is specified. Rasa will use the graph component's predict_action_probabilities to make predictions for the next action which should be run within a conversation.

    • ComponentType.POLICY_WITH_END_TO_END_SUPPORT: Component type for policies which require additional end-to-end features (see end-to-end training for more information). The end-to-end features are passed into the graph component's train and predict_action_probabilities as precomputations parameter. This graph component is run only during training if is_trainable=True. The graph component is always run during inference. Rasa will use the graph component's train method if is_trainable=True is specified. Rasa will use the graph component's predict_action_probabilities to make predictions for the next action which should be run within a conversation.

  • is_trainable: Specifies if the graph component is required to train itself before it can process training data for other dependent graph components or before it can make predictions

  • model_from: Specifies if a pretrained language model needs to be provided to the train, process_training_data and process methods of the graph component. These methods have to support the parameter model to receive the language model. Note that you still need to make sure that the graph component which provides this model is part of your model configuration. A common use case for this is if you want to expose the SpacyNLP language model to your other NLU components.

Using Custom Components in your Model Configuration

You can use custom graph components like any other NLU component or policy within your model configuration. The only change is that you have to specify the full module name instead of the class name only. The full module name depends on your module's location in relation to the specified PYTHONPATH. By default, Rasa adds the directory from where you run the CLI to the PYTHONPATH. If you e.g. run the CLI from /Users/<user>/my-rasa-project and your module MyComponent is in /Users/<user>/my-rasa-project/custom_components/my_component.py then the module path is custom_components.my_component.MyComponent. Everything except the name entry will be passed as config to your component.

config.yml
recipe: default.v1
language: en
pipeline:
# other NLU components
- name: your.custom.NLUComponent
setting_a: 0.01
setting_b: string_value
policies:
# other dialogue policies
- name: your.custom.Policy

Implementation Hints

Message Metadata

When you define metadata for your intent examples in your training data, your NLU component can access both the intent metadata and the intent example metadata during processing:

# in your component class
def process(self, message: Message, **kwargs: Any) -> None:
metadata = message.get("metadata")
print(metadata.get("intent"))
print(metadata.get("example"))

Sparse and Dense Message Features

If you create a custom message featurizer, you can return two different kind of features: sequence features and sentence features. The sequence features are a matrix of size (number-of-tokens x feature-dimension), i.e. the matrix contains a feature vector for every token in the sequence. The sentence features are represented by a matrix of size (1 x feature-dimension).

Examples of Custom Components

Dense Message Featurizer

The following is the example of a dense message featurizer which uses a pretrained model:

import numpy as np
import logging
from bpemb import BPEmb
from typing import Any, Text, Dict, List, Type
from rasa.engine.recipes.default_recipe import DefaultV1Recipe
from rasa.engine.graph import ExecutionContext, GraphComponent
from rasa.engine.storage.resource import Resource
from rasa.engine.storage.storage import ModelStorage
from rasa.nlu.featurizers.dense_featurizer.dense_featurizer import DenseFeaturizer
from rasa.nlu.tokenizers.tokenizer import Tokenizer
from rasa.shared.nlu.training_data.training_data import TrainingData
from rasa.shared.nlu.training_data.features import Features
from rasa.shared.nlu.training_data.message import Message
from rasa.nlu.constants import (
DENSE_FEATURIZABLE_ATTRIBUTES,
FEATURIZER_CLASS_ALIAS,
)
from rasa.shared.nlu.constants import (
TEXT,
TEXT_TOKENS,
FEATURE_TYPE_SENTENCE,
FEATURE_TYPE_SEQUENCE,
)
logger = logging.getLogger(__name__)
@DefaultV1Recipe.register(
DefaultV1Recipe.ComponentType.MESSAGE_FEATURIZER, is_trainable=False
)
class BytePairFeaturizer(DenseFeaturizer, GraphComponent):
@classmethod
def required_components(cls) -> List[Type]:
"""Components that should be included in the pipeline before this component."""
return [Tokenizer]
@staticmethod
def required_packages() -> List[Text]:
"""Any extra python dependencies required for this component to run."""
return ["bpemb"]
@staticmethod
def get_default_config() -> Dict[Text, Any]:
"""Returns the component's default config."""
return {
**DenseFeaturizer.get_default_config(),
# specifies the language of the subword segmentation model
"lang": None,
# specifies the dimension of the subword embeddings
"dim": None,
# specifies the vocabulary size of the segmentation model
"vs": None,
# if set to True and the given vocabulary size can't be loaded for the given
# model, the closest size is chosen
"vs_fallback": True,
}
def __init__(
self,
config: Dict[Text, Any],
name: Text,
) -> None:
"""Constructs a new byte pair vectorizer."""
super().__init__(name, config)
# The configuration dictionary is saved in `self._config` for reference.
self.model = BPEmb(
lang=self._config["lang"],
dim=self._config["dim"],
vs=self._config["vs"],
vs_fallback=self._config["vs_fallback"],
)
@classmethod
def create(
cls,
config: Dict[Text, Any],
model_storage: ModelStorage,
resource: Resource,
execution_context: ExecutionContext,
) -> GraphComponent:
"""Creates a new component (see parent class for full docstring)."""
return cls(config, execution_context.node_name)
def process(self, messages: List[Message]) -> List[Message]:
"""Processes incoming messages and computes and sets features."""
for message in messages:
for attribute in DENSE_FEATURIZABLE_ATTRIBUTES:
self._set_features(message, attribute)
return messages
def process_training_data(self, training_data: TrainingData) -> TrainingData:
"""Processes the training examples in the given training data in-place."""
self.process(training_data.training_examples)
return training_data
def _create_word_vector(self, document: Text) -> np.ndarray:
"""Creates a word vector from a text. Utility method."""
encoded_ids = self.model.encode_ids(document)
if encoded_ids:
return self.model.vectors[encoded_ids[0]]
return np.zeros((self.component_config["dim"],), dtype=np.float32)
def _set_features(self, message: Message, attribute: Text = TEXT) -> None:
"""Sets the features on a single message. Utility method."""
tokens = message.get(TEXT_TOKENS)
# If the message doesn't have tokens, we can't create features.
if not tokens:
return None
# We need to reshape here such that the shape is equivalent to that of sparsely
# generated features. Without it, it'd be a 1D tensor. We need 2D (n_utterance, n_dim).
text_vector = self._create_word_vector(document=message.get(TEXT)).reshape(
1, -1
)
word_vectors = np.array(
[self._create_word_vector(document=t.text) for t in tokens]
)
final_sequence_features = Features(
word_vectors,
FEATURE_TYPE_SEQUENCE,
attribute,
self._config[FEATURIZER_CLASS_ALIAS],
)
message.add_features(final_sequence_features)
final_sentence_features = Features(
text_vector,
FEATURE_TYPE_SENTENCE,
attribute,
self._config[FEATURIZER_CLASS_ALIAS],
)
message.add_features(final_sentence_features)
@classmethod
def validate_config(cls, config: Dict[Text, Any]) -> None:
"""Validates that the component is configured properly."""
if not config["lang"]:
raise ValueError("BytePairFeaturizer needs language setting via `lang`.")
if not config["dim"]:
raise ValueError(
"BytePairFeaturizer needs dimensionality setting via `dim`."
)
if not config["vs"]:
raise ValueError("BytePairFeaturizer needs a vector size setting via `vs`.")

Sparse Message Featurizer

The following is the example of a dense message featurizer which trains a new model:

import logging
from typing import Any, Text, Dict, List, Type
from sklearn.feature_extraction.text import TfidfVectorizer
from rasa.engine.recipes.default_recipe import DefaultV1Recipe
from rasa.engine.graph import ExecutionContext, GraphComponent
from rasa.engine.storage.resource import Resource
from rasa.engine.storage.storage import ModelStorage
from rasa.nlu.featurizers.sparse_featurizer.sparse_featurizer import SparseFeaturizer
from rasa.nlu.tokenizers.tokenizer import Tokenizer
from rasa.shared.nlu.training_data.training_data import TrainingData
from rasa.shared.nlu.training_data.features import Features
from rasa.shared.nlu.training_data.message import Message
from rasa.nlu.constants import (
DENSE_FEATURIZABLE_ATTRIBUTES,
FEATURIZER_CLASS_ALIAS,
)
from joblib import dump, load
from rasa.shared.nlu.constants import (
TEXT,
TEXT_TOKENS,
FEATURE_TYPE_SENTENCE,
FEATURE_TYPE_SEQUENCE,
)
logger = logging.getLogger(__name__)
@DefaultV1Recipe.register(
DefaultV1Recipe.ComponentType.MESSAGE_FEATURIZER, is_trainable=True
)
class TfIdfFeaturizer(SparseFeaturizer, GraphComponent):
@classmethod
def required_components(cls) -> List[Type]:
"""Components that should be included in the pipeline before this component."""
return [Tokenizer]
@staticmethod
def required_packages() -> List[Text]:
"""Any extra python dependencies required for this component to run."""
return ["sklearn"]
@staticmethod
def get_default_config() -> Dict[Text, Any]:
"""Returns the component's default config."""
return {
**SparseFeaturizer.get_default_config(),
"analyzer": "word",
"min_ngram": 1,
"max_ngram": 1,
}
def __init__(
self,
config: Dict[Text, Any],
name: Text,
model_storage: ModelStorage,
resource: Resource,
) -> None:
"""Constructs a new tf/idf vectorizer using the sklearn framework."""
super().__init__(name, config)
# Initialize the tfidf sklearn component
self.tfm = TfidfVectorizer(
analyzer=config["analyzer"],
ngram_range=(config["min_ngram"], config["max_ngram"]),
)
# We need to use these later when saving the trained component.
self._model_storage = model_storage
self._resource = resource
def train(self, training_data: TrainingData) -> Resource:
"""Trains the component from training data."""
texts = [e.get(TEXT) for e in training_data.training_examples if e.get(TEXT)]
self.tfm.fit(texts)
self.persist()
return self._resource
@classmethod
def create(
cls,
config: Dict[Text, Any],
model_storage: ModelStorage,
resource: Resource,
execution_context: ExecutionContext,
) -> GraphComponent:
"""Creates a new untrained component (see parent class for full docstring)."""
return cls(config, execution_context.node_name, model_storage, resource)
def _set_features(self, message: Message, attribute: Text = TEXT) -> None:
"""Sets the features on a single message. Utility method."""
tokens = message.get(TEXT_TOKENS)
# If the message doesn't have tokens, we can't create features.
if not tokens:
return None
# Make distinction between sentence and sequence features
text_vector = self.tfm.transform([message.get(TEXT)])
word_vectors = self.tfm.transform([t.text for t in tokens])
final_sequence_features = Features(
word_vectors,
FEATURE_TYPE_SEQUENCE,
attribute,
self._config[FEATURIZER_CLASS_ALIAS],
)
message.add_features(final_sequence_features)
final_sentence_features = Features(
text_vector,
FEATURE_TYPE_SENTENCE,
attribute,
self._config[FEATURIZER_CLASS_ALIAS],
)
message.add_features(final_sentence_features)
def process(self, messages: List[Message]) -> List[Message]:
"""Processes incoming message and compute and set features."""
for message in messages:
for attribute in DENSE_FEATURIZABLE_ATTRIBUTES:
self._set_features(message, attribute)
return messages
def process_training_data(self, training_data: TrainingData) -> TrainingData:
"""Processes the training examples in the given training data in-place."""
self.process(training_data.training_examples)
return training_data
def persist(self) -> None:
"""
Persist this model into the passed directory.
Returns the metadata necessary to load the model again. In this case; `None`.
"""
with self._model_storage.write_to(self._resource) as model_dir:
dump(self.tfm, model_dir / "tfidfvectorizer.joblib")
@classmethod
def load(
cls,
config: Dict[Text, Any],
model_storage: ModelStorage,
resource: Resource,
execution_context: ExecutionContext,
) -> GraphComponent:
"""Loads trained component from disk."""
try:
with model_storage.read_from(resource) as model_dir:
tfidfvectorizer = load(model_dir / "tfidfvectorizer.joblib")
component = cls(
config, execution_context.node_name, model_storage, resource
)
component.tfm = tfidfvectorizer
except (ValueError, FileNotFoundError):
logger.debug(
f"Couldn't load metadata for component '{cls.__name__}' as the persisted "
f"model data couldn't be loaded."
)
return component
@classmethod
def validate_config(cls, config: Dict[Text, Any]) -> None:
"""Validates that the component is configured properly."""
pass

NLU Meta Learners

Advanced use case

NLU Meta learners are an advanced use case. The following section is only relevant if you have a component that learns parameters based on the output of previous classifiers. For components that have manually set parameters or logic, you can create a component with is_trainable=False and not worry about the preceding classifiers.

NLU Meta learners are intent classifiers or entity extractors that use the predictions of other trained intent classifiers or entity extractors and try to improve upon their results. An example for a meta learner would be a component that averages the output of two previous intent classifiers or a fallback classifier that sets it's threshold according to the confidence of the intent classifier on training examples.

Conceptually, to built a trainable fallback classifier you first need to create that fallback classifier as a custom component:

from typing import Dict, Text, Any, List
from rasa.engine.graph import GraphComponent, ExecutionContext
from rasa.engine.recipes.default_recipe import DefaultV1Recipe
from rasa.engine.storage.resource import Resource
from rasa.engine.storage.storage import ModelStorage
from rasa.shared.nlu.training_data.message import Message
from rasa.shared.nlu.training_data.training_data import TrainingData
from rasa.nlu.classifiers.fallback_classifier import FallbackClassifier
@DefaultV1Recipe.register(
[DefaultV1Recipe.ComponentType.INTENT_CLASSIFIER], is_trainable=True
)
class MetaFallback(FallbackClassifier):
def __init__(
self,
config: Dict[Text, Any],
model_storage: ModelStorage,
resource: Resource,
execution_context: ExecutionContext,
) -> None:
super().__init__(config)
self._model_storage = model_storage
self._resource = resource
@classmethod
def create(
cls,
config: Dict[Text, Any],
model_storage: ModelStorage,
resource: Resource,
execution_context: ExecutionContext,
) -> FallbackClassifier:
"""Creates a new untrained component (see parent class for full docstring)."""
return cls(config, model_storage, resource, execution_context)
def train(self, training_data: TrainingData) -> Resource:
# Do something here with the messages
return self._resource

Next, you will need to create a custom intent classifier that is also a featurizer, as the classifiers' output needs to be consumed by another component downstream. For the custom intent classifier component you also need to define how its predictions should be added to the message data specifying the process_training_data method. Make sure to not overwrite the true labels for the intents. Here's a template that shows how to subclass DIET for this purpose:

from rasa.engine.recipes.default_recipe import DefaultV1Recipe
from rasa.shared.nlu.training_data.training_data import TrainingData
from rasa.nlu.classifiers.diet_classifier import DIETClassifier
@DefaultV1Recipe.register(
[DefaultV1Recipe.ComponentType.INTENT_CLASSIFIER,
DefaultV1Recipe.ComponentType.ENTITY_EXTRACTOR,
DefaultV1Recipe.ComponentType.MESSAGE_FEATURIZER], is_trainable=True
)
class DIETFeaturizer(DIETClassifier):
def process_training_data(self, training_data: TrainingData) -> TrainingData:
# classify and add the attributes to the messages on the training data
return training_data