langchain/agents/agent.py/AgentExecutor/save
class AgentExecutor:    def save(self, file_path: Union[Path, str]) -> None:
        """Raise error - saving not supported for Agent Executors."""
        raise ValueError(
            "Saving not supported for agent executors. "
            "If you are trying to save the agent, please use the "
            "`.save_agent(...)`"
        )