langchain/llms/base.py/BaseLLM/_call_async
class BaseLLM:    async def _call_async(
        self, prompt: str, stop: Optional[List[str]] = None, callbacks: Callbacks = None
    ) -> str:
        """Check Cache and run the LLM on the given prompt and input."""
        result = await self.agenerate([prompt], stop=stop, callbacks=callbacks)
        return result.generations[0][0].text