"""An optional function to get a string of the chat history.
    If None is provided, will use a default."""
    class Config:
        """Configuration for this pydantic object."""
        extra = Extra.forbid
        arbitrary_types_allowed = True
        allow_population_by_field_name = True
    @property
    def input_keys(self) -> List[str]:
        """Input keys."""
        return ["question", "chat_history"]
    @property
    def output_keys(self) -> List[str]:
        """Return the output keys.
        :meta private:
        """
        _output_keys = [self.output_key]
        if self.return_source_documents:
            _output_keys = _output_keys + ["source_documents"]
        if self.return_generated_question:
            _output_keys = _output_keys + ["generated_question"]
        return _output_keys
    @abstractmethod
    def _get_docs(
        self,
        question: str,
        inputs: Dict[str, Any],
        *,
        run_manager: CallbackManagerForChainRun,
    ) -> List[Document]:
        """Get docs."""
    def _call(
        self,
        inputs: Dict[str, Any],
        run_manager: Optional[CallbackManagerForChainRun] = None,
    ) -> Dict[str, Any]:
        _run_manager = run_manager or CallbackManagerForChainRun.get_noop_manager()
        question = inputs["question"]
        get_chat_history = self.get_chat_history or _get_chat_history
        chat_history_str = get_chat_history(inputs["chat_history"])
        if chat_history_str:
            callbacks = _run_manager.get_child()
            new_question = self.question_generator.run(
                question=question, chat_history=chat_history_str, callbacks=callbacks
            )
        else: