langchain/callbacks/stdout.py/StdOutCallbackHandler/on_text
class StdOutCallbackHandler:    def on_text(
        self,
        text: str,
        color: Optional[str] = None,
        end: str = "",
        **kwargs: Any,
    ) -> None:
        """Run when agent ends."""
        print_text(text, color=color if color else self.color, end=end)