langchain/llms/base.py/LLM/_acall
class LLM:    async def _acall(
        self,
        prompt: str,
        stop: Optional[List[str]] = None,
        run_manager: Optional[AsyncCallbackManagerForLLMRun] = None,
    ) -> str:
        """Run the LLM on the given prompt and input."""
        raise NotImplementedError("Async generation not implemented for this LLM.")