code: def init_from_datastore(self):
      
      self._data = {}
      client = self._datastore_client
      for entity in client.query_fetch(kind=KIND_CLASSIFICATION_BATCH):
        class_batch_id = entity.key.flat_path[-1]
        self.data[class_batch_id] = dict(entity)
docs: Initializes data by reading it from the datastore.