langchain/tools/youtube/search.py/YouTubeSearchTool/_arun
class YouTubeSearchTool:    async def _arun(
        self,
        query: str,
        run_manager: Optional[AsyncCallbackManagerForToolRun] = None,
    ) -> str:
        """Use the tool asynchronously."""
        raise NotImplementedError("YouTubeSearchTool  does not yet support async")