code: def _is_empty_cache_record(self, rec):
          
          # these are taken from DataQuery.query_one_table()
          for k in [
              'by_version',
              'by_file_type',
              'by_installer',
              'by_implementation',
              'by_system',
              'by_distro',
              'by_country'
          ]:
              if k in rec and len(rec[k]) > 0:
                  return False
          return True
docs: Return True if the specified cache record has no data, False otherwise.
  
          :param rec: cache record returned by :py:meth:`~._cache_get`
          :type rec: dict
          :return: True if record is empty, False otherwise
          :rtype: bool