langchain/tools/google_serper/tool.py/GoogleSerperRun/_arun
class GoogleSerperRun:    async def _arun(
        self,
        query: str,
        run_manager: Optional[AsyncCallbackManagerForToolRun] = None,
    ) -> str:
        """Use the tool asynchronously."""
        return (await self.api_wrapper.arun(query)).__str__()