langchain/document_loaders/url.py/UnstructuredURLLoader/load
class UnstructuredURLLoader:    def load(self) -> List[Document]:
        """Load file."""
        from unstructured.partition.auto import partition
        from unstructured.partition.html import partition_html

        docs: List[Document] = list()
        for url in self.urls:
            try:
                if self.__is_non_html_available():
                    if self.__is_headers_available_for_non_html():
                        elements = partition(
                            url=url, headers=self.headers, **self.unstructured_kwargs
                        )
                    else:
                        elements = partition(url=url, **self.unstructured_kwargs)
                else:
                    if self.__is_headers_available_for_html():
                        elements = partition_html(
                            url=url, headers=self.headers, **self.unstructured_kwargs
                        )
                    else:
                        elements = partition_html(url=url, **self.unstructured_kwargs)
            except Exception as e:
                if self.continue_on_failure:
                    logger.error(f"Error fetching or processing {url}, exeption: {e}")
                    continue
                else:
                    raise e

            if self.mode == "single":
                text = "\n\n".join([str(el) for el in elements])
                metadata = {"source": url}
                docs.append(Document(page_content=text, metadata=metadata))
            elif self.mode == "elements":
                for element in elements:
                    metadata = element.metadata.to_dict()
                    metadata["category"] = element.category
                    docs.append(Document(page_content=str(element), metadata=metadata))

        return docs