Source code for langchain.chains.combine_documents.map_rerank
"""Combining documents by mapping a chain over them first, then reranking results."""
from __future__ import annotations
from typing import Any, Dict, List, Optional, Sequence, Tuple, Union, cast
from langchain.callbacks.manager import Callbacks
from langchain.chains.combine_documents.base import BaseCombineDocumentsChain
from langchain.chains.llm import LLMChain
from langchain.docstore.document import Document
from langchain.output_parsers.regex import RegexParser
from langchain.pydantic_v1 import BaseModel, Extra, create_model, root_validator
[docs]class MapRerankDocumentsChain(BaseCombineDocumentsChain):
    """Combining documents by mapping a chain over them, then reranking results.
    This algorithm calls an LLMChain on each input document. The LLMChain is expected
    to have an OutputParser that parses the result into both an answer (`answer_key`)
    and a score (`rank_key`). The answer with the highest score is then returned.
    Example:
        .. code-block:: python
            from langchain.chains import StuffDocumentsChain, LLMChain
            from langchain.prompts import PromptTemplate
            from langchain.llms import OpenAI
            from langchain.output_parsers.regex import RegexParser
            document_variable_name = "context"
            llm = OpenAI()
            # The prompt here should take as an input variable the
            # `document_variable_name`
            # The actual prompt will need to be a lot more complex, this is just
            # an example.
            prompt_template = (
                "Use the following context to tell me the chemical formula "
                "for water. Output both your answer and a score of how confident "
                "you are. Context: {content}"
            )