docs: def get_data_excel_xml(file_name, file_contents=None, on_demand=False):
      '''
      Loads xml excel format files.
  
      Args:
          file_name: The name of the local file, or the holder for the
              extension type when the file_contents are supplied.
          file_contents: The file-like object holding contents of file_name.
              If left as None, then file_name is directly loaded.
          on_demand: Requests that a yielder be used in place of a full data
              copy (will be ignored).
      '''
      # NOTE this method is inefficient and uses code that's not of the highest quality
      if file_contents:
          xml_file = BytesIO(file_contents)
      else:
          xml_file = file_name
      book = xmlparse.ParseExcelXMLFile(xml_file)
      row_builder = lambda s, r: list(s.row_values(r))
      return [XMLSheetYielder(book, index, row_builder) for index in range(len(book))]