docs: def required_attributes(element, *attributes):
      """Check element for required attributes. Raise ``NotValidXmlException`` on error.
  
      :param element: ElementTree element
      :param attributes: list of attributes names to check
      :raises NotValidXmlException: if some argument is missing
      """
      if not reduce(lambda still_valid, param: still_valid and param in element.attrib, attributes, True):
          raise NotValidXmlException(msg_err_missing_attributes(element.tag, *attributes))