Haystack docs home page

🎉 We are working to make this website better, stay tuned. In the meantime, have a look at our up to date API Reference section in the new docs.

Module base

BaseGenerator

class BaseGenerator(BaseComponent)

Abstract class for Generators

BaseGenerator.predict

@abstractmethod
def predict(query: str, documents: List[Document],
            top_k: Optional[int]) -> Dict

Abstract method to generate answers.

Arguments:

  • query: Query
  • documents: Related documents (e.g. coming from a retriever) that the answer shall be conditioned on.
  • top_k: Number of returned answers

Returns:

Generated answers plus additional infos in a dict

BaseGenerator.predict_batch

def predict_batch(queries: List[str],
                  documents: Union[List[Document], List[List[Document]]],
                  top_k: Optional[int] = None,
                  batch_size: Optional[int] = None)

Generate the answer to the input queries. The generation will be conditioned on the supplied documents.

These documents can for example be retrieved via the Retriever.

  • If you provide a list containing a single query...

    • ... and a single list of Documents, the query will be applied to each Document individually.
    • ... and a list of lists of Documents, the query will be applied to each list of Documents and the Answers will be aggregated per Document list.
  • If you provide a list of multiple queries...

    • ... and a single list of Documents, each query will be applied to each Document individually.
    • ... and a list of lists of Documents, each query will be applied to its corresponding list of Documents and the Answers will be aggregated per query-Document pair.

Arguments:

  • queries: List of queries.
  • documents: Related documents (e.g. coming from a retriever) that the answer shall be conditioned on. Can be a single list of Documents or a list of lists of Documents.
  • top_k: Number of returned answers per query.
  • batch_size: Not applicable.

Returns:

Generated answers plus additional infos in a dict like this:

|     {'queries': 'who got the first nobel prize in physics',
|      'answers':
|          [{'query': 'who got the first nobel prize in physics',
|            'answer': ' albert einstein',
|            'meta': { 'doc_ids': [...],
|                      'doc_scores': [80.42758 ...],
|                      'doc_probabilities': [40.71379089355469, ...
|                      'content': ['Albert Einstein was a ...]
|                      'titles': ['"Albert Einstein"', ...]
|      }}]}

Module transformers

RAGenerator

class RAGenerator(BaseGenerator)

Implementation of Facebook's Retrieval-Augmented Generator (https://arxiv.org/abs/2005.11401) based on HuggingFace's transformers (https://huggingface.co/transformers/model_doc/rag.html).

Instead of "finding" the answer within a document, these models generate the answer. In that sense, RAG follows a similar approach as GPT-3 but it comes with two huge advantages for real-world applications: a) it has a manageable model size b) the answer generation is conditioned on retrieved documents, i.e. the model can easily adjust to domain documents even after training has finished (in contrast: GPT-3 relies on the web data seen during training)

Example

|     query = "who got the first nobel prize in physics?"
|
|     # Retrieve related documents from retriever
|     retrieved_docs = retriever.retrieve(query=query)
|
|     # Now generate answer from query and retrieved documents
|     generator.predict(
|        query=query,
|        documents=retrieved_docs,
|        top_k=1
|     )
|
|     # Answer
|
|     {'query': 'who got the first nobel prize in physics',
|      'answers':
|          [{'query': 'who got the first nobel prize in physics',
|            'answer': ' albert einstein',
|            'meta': { 'doc_ids': [...],
|                      'doc_scores': [80.42758 ...],
|                      'doc_probabilities': [40.71379089355469, ...
|                      'content': ['Albert Einstein was a ...]
|                      'titles': ['"Albert Einstein"', ...]
|      }}]}

RAGenerator.__init__

def __init__(model_name_or_path: str = "facebook/rag-token-nq",
             model_version: Optional[str] = None,
             retriever: Optional[DensePassageRetriever] = None,
             generator_type: str = "token",
             top_k: int = 2,
             max_length: int = 200,
             min_length: int = 2,
             num_beams: int = 2,
             embed_title: bool = True,
             prefix: Optional[str] = None,
             use_gpu: bool = True,
             progress_bar: bool = True,
             use_auth_token: Optional[Union[str, bool]] = None,
             devices: Optional[List[Union[str, torch.device]]] = None)

Load a RAG model from Transformers along with passage_embedding_model.

See https://huggingface.co/transformers/model_doc/rag.html for more details

Arguments:

  • model_name_or_path: Directory of a saved model or the name of a public model e.g. 'facebook/rag-token-nq', 'facebook/rag-sequence-nq'. See https://huggingface.co/models for full list of available models.
  • model_version: The version of model to use from the HuggingFace model hub. Can be tag name, branch name, or commit hash.
  • retriever: DensePassageRetriever used to embedded passages for the docs passed to predict(). This is optional and is only needed if the docs you pass don't already contain embeddings in Document.embedding.
  • generator_type: Which RAG generator implementation to use ("token" or "sequence")
  • top_k: Number of independently generated text to return
  • max_length: Maximum length of generated text
  • min_length: Minimum length of generated text
  • num_beams: Number of beams for beam search. 1 means no beam search.
  • embed_title: Embedded the title of passage while generating embedding
  • prefix: The prefix used by the generator's tokenizer.
  • use_gpu: Whether to use GPU. Falls back on CPU if no GPU is available.
  • progress_bar: Whether to show a tqdm progress bar or not.
  • use_auth_token: The API token used to download private models from Huggingface. If this parameter is set to True, then the token generated when running transformers-cli login (stored in ~/.huggingface) will be used. Additional information can be found here https://huggingface.co/transformers/main_classes/model.html#transformers.PreTrainedModel.from_pretrained
  • devices: List of torch devices (e.g. cuda, cpu, mps) to limit inference to specific devices. A list containing torch device objects and/or strings is supported (For example [torch.device('cuda:0'), "mps", "cuda:1"]). When specifying use_gpu=False the devices parameter is not used and a single cpu device is used for inference.

RAGenerator.predict

def predict(query: str,
            documents: List[Document],
            top_k: Optional[int] = None) -> Dict

Generate the answer to the input query. The generation will be conditioned on the supplied documents.

These documents can for example be retrieved via the Retriever.

Arguments:

  • query: Query
  • documents: Related documents (e.g. coming from a retriever) that the answer shall be conditioned on.
  • top_k: Number of returned answers

Returns:

Generated answers plus additional infos in a dict like this:

|     {'query': 'who got the first nobel prize in physics',
|      'answers':
|          [{'query': 'who got the first nobel prize in physics',
|            'answer': ' albert einstein',
|            'meta': { 'doc_ids': [...],
|                      'doc_scores': [80.42758 ...],
|                      'doc_probabilities': [40.71379089355469, ...
|                      'content': ['Albert Einstein was a ...]
|                      'titles': ['"Albert Einstein"', ...]
|      }}]}

Seq2SeqGenerator

class Seq2SeqGenerator(BaseGenerator)

A generic sequence-to-sequence generator based on HuggingFace's transformers.

This generator supports all Text2Text models from the Hugging Face hub. If the primary interface for the model specified by model_name_or_path constructor parameter is AutoModelForSeq2SeqLM from Hugging Face, then you can use it in this Generator.

Moreover, as language models prepare model input in their specific encoding, each model specified with model_name_or_path parameter in this Seq2SeqGenerator should have an accompanying model input converter that takes care of prefixes, separator tokens etc. By default, we provide model input converters for a few well-known seq2seq language models (e.g. ELI5). It is the responsibility of Seq2SeqGenerator user to ensure an appropriate model input converter is either already registered or specified on a per-model basis in the Seq2SeqGenerator constructor.

For mode details on custom model input converters refer to _BartEli5Converter

For a list of all text2text-generation models, see the Hugging Face Model Hub

Example

|     query = "Why is Dothraki language important?"
|
|     # Retrieve related documents from retriever
|     retrieved_docs = retriever.retrieve(query=query)
|
|     # Now generate answer from query and retrieved documents
|     generator.predict(
|        query=query,
|        documents=retrieved_docs,
|        top_k=1
|     )
|
|     # Answer
|
|     {'query': 'who got the first nobel prize in physics',
|      'answers':
|          [{'query': 'who got the first nobel prize in physics',
|            'answer': ' albert einstein',
|            'meta': { 'doc_ids': [...],
|                      'doc_scores': [80.42758 ...],
|                      'doc_probabilities': [40.71379089355469, ...
|                      'content': ['Albert Einstein was a ...]
|                      'titles': ['"Albert Einstein"', ...]
|      }}]}

Seq2SeqGenerator.__init__

def __init__(model_name_or_path: str,
             input_converter: Optional[Callable] = None,
             top_k: int = 1,
             max_length: int = 200,
             min_length: int = 2,
             num_beams: int = 8,
             use_gpu: bool = True,
             progress_bar: bool = True,
             use_auth_token: Optional[Union[str, bool]] = None,
             devices: Optional[List[Union[str, torch.device]]] = None)

Arguments:

  • model_name_or_path: a HF model name for auto-regressive language model like GPT2, XLNet, XLM, Bart, T5 etc
  • input_converter: an optional Callable to prepare model input for the underlying language model specified in model_name_or_path parameter. The required call method signature for the Callable is: call(tokenizer: PreTrainedTokenizer, query: str, documents: List[Document], top_k: Optional[int] = None) -> BatchEncoding:
  • top_k: Number of independently generated text to return
  • max_length: Maximum length of generated text
  • min_length: Minimum length of generated text
  • num_beams: Number of beams for beam search. 1 means no beam search.
  • use_gpu: Whether to use GPU or the CPU. Falls back on CPU if no GPU is available.
  • progress_bar: Whether to show a tqdm progress bar or not.
  • use_auth_token: The API token used to download private models from Huggingface. If this parameter is set to True, then the token generated when running transformers-cli login (stored in ~/.huggingface) will be used. Additional information can be found here https://huggingface.co/transformers/main_classes/model.html#transformers.PreTrainedModel.from_pretrained
  • devices: List of torch devices (e.g. cuda, cpu, mps) to limit inference to specific devices. A list containing torch device objects and/or strings is supported (For example [torch.device('cuda:0'), "mps", "cuda:1"]). When specifying use_gpu=False the devices parameter is not used and a single cpu device is used for inference.

Seq2SeqGenerator.predict

def predict(query: str,
            documents: List[Document],
            top_k: Optional[int] = None) -> Dict

Generate the answer to the input query. The generation will be conditioned on the supplied documents.

These document can be retrieved via the Retriever or supplied directly via predict method.

Arguments:

  • query: Query
  • documents: Related documents (e.g. coming from a retriever) that the answer shall be conditioned on.
  • top_k: Number of returned answers

Returns:

Generated answers

Module openai

OpenAIAnswerGenerator

class OpenAIAnswerGenerator(BaseGenerator)

Uses the GPT-3 models from the OpenAI API to generate Answers based on the Documents it receives. The Documents can come from a Retriever or you can supply them manually.

To use this Node, you need an API key from an active OpenAI account. You can sign-up for an account on the OpenAI API website.

OpenAIAnswerGenerator.__init__

def __init__(api_key: str,
             model: str = "text-curie-001",
             max_tokens: int = 13,
             top_k: int = 5,
             temperature: float = 0.2,
             presence_penalty: float = -2.0,
             frequency_penalty: float = -2.0,
             examples_context: Optional[str] = None,
             examples: Optional[List] = None,
             stop_words: Optional[List] = None,
             progress_bar: bool = True)

Arguments:

  • api_key: Your API key from OpenAI. It is required for this node to work.
  • model: ID of the engine to use for generating the answer. You can select one of "text-ada-001", "text-babbage-001", "text-curie-001", or "text-davinci-002" (from worst to best and from cheapest to most expensive). For more information about the models, refer to the OpenAI Documentation.
  • max_tokens: The maximum number of tokens allowed for the generated Answer.
  • top_k: Number of generated Answers.
  • temperature: What sampling temperature to use. Higher values mean the model will take more risks and value 0 (argmax sampling) works better for scenarios with a well-defined Answer.
  • presence_penalty: Number between -2.0 and 2.0. Positive values penalize new tokens based on whether they have already appeared in the text. This increases the model's likelihood to talk about new topics.
  • frequency_penalty: Number between -2.0 and 2.0. Positive values penalize new tokens based on their existing frequency in the text so far, decreasing the model's likelihood to repeat the same line verbatim.
  • examples_context: A text snippet containing the contextual information used to generate the Answers for the examples you provide. If not supplied, the default from OpenAPI docs is used: "In 2017, U.S. life expectancy was 78.6 years."
  • examples: List of (question, answer) pairs that helps steer the model towards the tone and answer format you'd like. We recommend adding 2 to 3 examples. If not supplied, the default from OpenAPI docs is used: [["What is human life expectancy in the United States?", "78 years."]]
  • stop_words: Up to 4 sequences where the API stops generating further tokens. The returned text does not contain the stop sequence. If you don't provide it, the default from OpenAPI docs is used: ["\n", "<|endoftext|>"]

OpenAIAnswerGenerator.predict

def predict(query: str,
            documents: List[Document],
            top_k: Optional[int] = None)

Use the loaded QA model to generate Answers for a query based on the Documents it receives.

Returns dictionaries containing Answers. Note that OpenAI doesn't return scores for those Answers.

Example:

|{
   |    'query': 'Who is the father of Arya Stark?',
   |    'answers':[Answer(
   |                 'answer': 'Eddard,',
   |                 'score': None,
   |                 ),...
   |              ]
   |}

Arguments:

  • query: The query you want to provide. It's a string.
  • documents: List of Documents in which to search for the Answer.
  • top_k: The maximum number of Answers to return.

Returns:

Dictionary containing query and Answers.