langchain/tools/searx_search/tool.py/SearxSearchResults/_arun
class SearxSearchResults:    async def _arun(
        self,
        query: str,
        run_manager: Optional[AsyncCallbackManagerForToolRun] = None,
    ) -> str:
        """Use the tool asynchronously."""
        return (await self.wrapper.aresults(query, self.num_results)).__str__()