base.py — langchain Source File

Source Code

"""Base interface for chains combining documents."""

from abc import ABC, abstractmethod
from typing import Any

from langchain_core._api import deprecated
from langchain_core.callbacks import (
    AsyncCallbackManagerForChainRun,
    CallbackManagerForChainRun,
)
from langchain_core.documents import Document
from langchain_core.prompts import BasePromptTemplate, PromptTemplate
from langchain_core.runnables.config import RunnableConfig
from langchain_core.utils.pydantic import create_model
from langchain_text_splitters import RecursiveCharacterTextSplitter, TextSplitter
from pydantic import BaseModel, Field
from typing_extensions import override

from langchain_classic.chains.base import Chain

DEFAULT_DOCUMENT_SEPARATOR = "\n\n"
DOCUMENTS_KEY = "context"
DEFAULT_DOCUMENT_PROMPT = PromptTemplate.from_template("{page_content}")


def _validate_prompt(prompt: BasePromptTemplate, document_variable_name: str) -> None:
    if document_variable_name not in prompt.input_variables:
        msg = (
            f"Prompt must accept {document_variable_name} as an input variable. "
            f"Received prompt with input variables: {prompt.input_variables}"
        )
        raise ValueError(msg)


class BaseCombineDocumentsChain(Chain, ABC):
    """Base interface for chains combining documents.

    Subclasses of this chain deal with combining documents in a variety of
    ways. This base class exists to add some uniformity in the interface these types
    of chains should expose. Namely, they expect an input key related to the documents
    to use (default `input_documents`), and then also expose a method to calculate
    the length of a prompt from documents (useful for outside callers to use to
    determine whether it's safe to pass a list of documents into this chain or whether
    that will be longer than the context length).
    """

    input_key: str = "input_documents"
    output_key: str = "output_text"

    @override
    def get_input_schema(
        self,
        config: RunnableConfig | None = None,
    ) -> type[BaseModel]:
        return create_model(
            "CombineDocumentsInput",
            **{self.input_key: (list[Document], None)},
        )

    @override
// ... (219 more lines)