langchain/callbacks/stdout.py/StdOutCallbackHandler/on_agent_finish
class StdOutCallbackHandler:    def on_agent_finish(
        self, finish: AgentFinish, color: Optional[str] = None, **kwargs: Any
    ) -> None:
        """Run on agent end."""
        print_text(finish.log, color=color if self.color else color, end="\n")