langchain/llms/openai.py/OpenAIChat/_agenerate
class OpenAIChat:    async def _agenerate(
        self,
        prompts: List[str],
        stop: Optional[List[str]] = None,
        run_manager: Optional[AsyncCallbackManagerForLLMRun] = None,
    ) -> LLMResult:
        messages, params = self._get_chat_params(prompts, stop)
        if self.streaming:
            response = ""
            params["stream"] = True
            async for stream_resp in await acompletion_with_retry(
                self, messages=messages, **params
            ):
                token = stream_resp["choices"][0]["delta"].get("content", "")
                response += token
                if run_manager:
                    await run_manager.on_llm_new_token(
                        token,
                    )
            return LLMResult(
                generations=[[Generation(text=response)]],
            )
        else:
            full_response = await acompletion_with_retry(
                self, messages=messages, **params
            )
            llm_output = {
                "token_usage": full_response["usage"],
                "model_name": self.model_name,
            }
            return LLMResult(
                generations=[
                    [Generation(text=full_response["choices"][0]["message"]["content"])]
                ],
                llm_output=llm_output,
            )