Source code for langchain.chains.combine_documents.base
"""Base interface for chains combining documents."""
from abc import ABC, abstractmethod
from typing import Any, Dict, List, Optional, Tuple
from pydantic import Field
from langchain.callbacks.manager import (
    AsyncCallbackManagerForChainRun,
    CallbackManagerForChainRun,
)
from langchain.chains.base import Chain
from langchain.docstore.document import Document
from langchain.prompts.base import BasePromptTemplate
from langchain.text_splitter import RecursiveCharacterTextSplitter, TextSplitter
def format_document(doc: Document, prompt: BasePromptTemplate) -> str:
    """Format a document into a string based on a prompt template."""
    base_info = {"page_content": doc.page_content}
    base_info.update(doc.metadata)
    missing_metadata = set(prompt.input_variables).difference(base_info)
    if len(missing_metadata) > 0:
        required_metadata = [
            iv for iv in prompt.input_variables if iv != "page_content"
        ]
        raise ValueError(
            f"Document prompt requires documents to have metadata variables: "
            f"{required_metadata}. Received document with missing metadata: "
            f"{list(missing_metadata)}."
        )
    document_info = {k: base_info[k] for k in prompt.input_variables}
    return prompt.format(**document_info)
class BaseCombineDocumentsChain(Chain, ABC):
    """Base interface for chains combining documents."""
    input_key: str = "input_documents"  #: :meta private:
    output_key: str = "output_text"  #: :meta private:
    @property
    def input_keys(self) -> List[str]:
        """Expect input key.
        :meta private:
        """
        return [self.input_key]
    @property
rtdocs_stable/api.python.langchain.com/en/stable/_modules/langchain/chains/combine_documents/base.html