langchain/document_loaders/web_base.py/WebBaseLoader/scrape_all
class WebBaseLoader:    def scrape_all(self, urls: List[str], parser: Union[str, None] = None) -> List[Any]:
        """Fetch all urls, then return soups for all results."""
        from bs4 import BeautifulSoup

        results = asyncio.run(self.fetch_all(urls))
        final_results = []
        for i, result in enumerate(results):
            url = urls[i]
            if parser is None:
                if url.endswith(".xml"):
                    parser = "xml"
                else:
                    parser = self.default_parser
                self._check_parser(parser)
            final_results.append(BeautifulSoup(result, parser))

        return final_results