langchain/callbacks/manager.py/CallbackManagerForChainRun/on_chain_end
class CallbackManagerForChainRun:    def on_chain_end(self, outputs: Dict[str, Any], **kwargs: Any) -> None:
        """Run when chain ends running."""
        _handle_event(
            self.handlers,
            "on_chain_end",
            "ignore_chain",
            outputs,
            run_id=self.run_id,
            parent_run_id=self.parent_run_id,
            **kwargs,
        )