def remove_deprecated_dashboard_data(self, model_type):
    query = model_type.query()
    entities = query.fetch(self.DASHBOARD_BATCH)
    counter = 0
    for entity in entities:
      if not hasattr(entity, "timestamp"):
        entity.key.delete()
        counter += 1
    if counter > 0:
      logging.warning("Removed {0} deprecated {1} dashboard entities".format(
        counter, entity._get_kind()))
Remove entities that do not have timestamps in Dashboard data. 
dataset/ETHPy150Open AppScale/appscale/AppDB/groomer.py/DatastoreGroomer.remove_deprecated_dashboard_data