langchain/tools/playwright/navigate_back.py/NavigateBackTool/_arun
class NavigateBackTool:    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)
        response = await page.go_back()

        if response:
            return (
                f"Navigated back to the previous page with URL '{response.url}'."
                f" Status code {response.status}"
            )
        else:
            return "Unable to navigate back; no previous page in the history"