langchain/tools/playwright/current_page.py/CurrentWebPageTool/_arun
class CurrentWebPageTool:    async def _arun(
        self,
        run_manager: Optional[AsyncCallbackManagerForToolRun] = None,
    ) -> str:
        """Use the tool."""
        if self.async_browser is None:
            raise ValueError(f"Asynchronous browser not provided to {self.name}")
        page = await aget_current_page(self.async_browser)
        return str(page.url)