langchain/callbacks/comet_ml_callback.py/CometCallbackHandler/on_llm_new_token
class CometCallbackHandler:    def on_llm_new_token(self, token: str, **kwargs: Any) -> None:
        """Run when LLM generates a new token."""
        self.step += 1
        self.llm_streams += 1

        resp = self._init_resp()
        resp.update({"action": "on_llm_new_token", "token": token})
        resp.update(self.get_custom_callback_meta())

        self.action_records.append(resp)