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