ReduceDocumentsChain

Example:

from langchain_classic.chains import (
    StuffDocumentsChain,
    LLMChain,
    ReduceDocumentsChain,
)
from langchain_core.prompts import PromptTemplate
from langchain_openai import OpenAI

# This controls how each document will be formatted. Specifically,
# it will be passed to `format_document` - see that function for more
# details.
document_prompt = PromptTemplate(
    input_variables=["page_content"], template="{page_content}"
)
document_variable_name = "context"
model = OpenAI()
# The prompt here should take as an input variable the
# `document_variable_name`
prompt = PromptTemplate.from_template("Summarize this content: {context}")
llm_chain = LLMChain(llm=model, prompt=prompt)
combine_documents_chain = StuffDocumentsChain(
    llm_chain=llm_chain,
    document_prompt=document_prompt,
    document_variable_name=document_variable_name,
)
chain = ReduceDocumentsChain(
    combine_documents_chain=combine_documents_chain,
)
# If we wanted to, we could also pass in collapse_documents_chain
# which is specifically aimed at collapsing documents BEFORE
# the final call.
prompt = PromptTemplate.from_template("Collapse this content: {context}")
llm_chain = LLMChain(llm=model, prompt=prompt)
collapse_documents_chain = StuffDocumentsChain(
    llm_chain=llm_chain,
    document_prompt=document_prompt,
    document_variable_name=document_variable_name,
)
chain = ReduceDocumentsChain(
    combine_documents_chain=combine_documents_chain,
    collapse_documents_chain=collapse_documents_chain,
)