langchain/document_loaders/epub.py/UnstructuredEPubLoader/_get_elements
class UnstructuredEPubLoader:    def _get_elements(self) -> List:
        min_unstructured_version = "0.5.4"
        if not satisfies_min_unstructured_version(min_unstructured_version):
            raise ValueError(
                "Partitioning epub files is only supported in "
                f"unstructured>={min_unstructured_version}."
            )
        from unstructured.partition.epub import partition_epub

        return partition_epub(filename=self.file_path, **self.unstructured_kwargs)