langchain/callbacks/manager.py/AsyncCallbackManagerForLLMRun/on_llm_new_token
class AsyncCallbackManagerForLLMRun:    async def on_llm_new_token(
        self,
        token: str,
        **kwargs: Any,
    ) -> None:
        """Run when LLM generates a new token."""
        await _ahandle_event(
            self.handlers,
            "on_llm_new_token",
            "ignore_llm",
            token,
            run_id=self.run_id,
            parent_run_id=self.parent_run_id,
            **kwargs,
        )