langchain/chains/question_answering/__init__.py/_load_stuff_chain
def _load_stuff_chain(
    llm: BaseLanguageModel,
    prompt: Optional[BasePromptTemplate] = None,
    document_variable_name: str = "context",
    verbose: Optional[bool] = None,
    callback_manager: Optional[BaseCallbackManager] = None,
    **kwargs: Any,
) -> StuffDocumentsChain:
    _prompt = prompt or stuff_prompt.PROMPT_SELECTOR.get_prompt(llm)
    llm_chain = LLMChain(
        llm=llm, prompt=_prompt, verbose=verbose, callback_manager=callback_manager
    )
    # TODO: document prompt
    return StuffDocumentsChain(
        llm_chain=llm_chain,
        document_variable_name=document_variable_name,
        verbose=verbose,
        callback_manager=callback_manager,
        **kwargs,
    )