Load document from xml using line offset information.
        This is much slower than _get_doc_by_raw_offset but should
        work everywhere.

def _get_doc_by_line_offset(self, doc_id):
        """
        Load document from xml using line offset information.
        This is much slower than _get_doc_by_raw_offset but should
        work everywhere.
        """
        bounds = self._get_meta()[str(doc_id)].bounds
        return xml_utils.load_chunk(self.filename, bounds, slow=True)