langchain/memory/chat_message_histories/zep.py/ZepChatMessageHistory/_get_memory
class ZepChatMessageHistory:    def _get_memory(self) -> Optional[Memory]:
        """Retrieve memory from Zep"""
        from zep_python import NotFoundError

        try:
            zep_memory: Memory = self.zep_client.get_memory(self.session_id)
        except NotFoundError:
            logger.warning(
                f"Session {self.session_id} not found in Zep. Returning None"
            )
            return None
        return zep_memory