langchain/chains/loading.py/_load_refine_documents_chain
def _load_refine_documents_chain(config: dict, **kwargs: Any) -> RefineDocumentsChain:
    if "initial_llm_chain" in config:
        initial_llm_chain_config = config.pop("initial_llm_chain")
        initial_llm_chain = load_chain_from_config(initial_llm_chain_config)
    elif "initial_llm_chain_path" in config:
        initial_llm_chain = load_chain(config.pop("initial_llm_chain_path"))
    else:
        raise ValueError(
            "One of `initial_llm_chain` or `initial_llm_chain_config` must be present."
        )
    if "refine_llm_chain" in config:
        refine_llm_chain_config = config.pop("refine_llm_chain")
        refine_llm_chain = load_chain_from_config(refine_llm_chain_config)
    elif "refine_llm_chain_path" in config:
        refine_llm_chain = load_chain(config.pop("refine_llm_chain_path"))
    else:
        raise ValueError(
            "One of `refine_llm_chain` or `refine_llm_chain_config` must be present."
        )
    if "document_prompt" in config:
        prompt_config = config.pop("document_prompt")
        document_prompt = load_prompt_from_config(prompt_config)
    elif "document_prompt_path" in config:
        document_prompt = load_prompt(config.pop("document_prompt_path"))
    return RefineDocumentsChain(
        initial_llm_chain=initial_llm_chain,
        refine_llm_chain=refine_llm_chain,
        document_prompt=document_prompt,
        **config,
    )