langchain/chains/conversational_retrieval/base.py/BaseConversationalRetrievalChain/save
class BaseConversationalRetrievalChain:    def save(self, file_path: Union[Path, str]) -> None:
        if self.get_chat_history:
            raise ValueError("Chain not savable when `get_chat_history` is not None.")
        super().save(file_path)