code: def _write_single_batch_images_internal(self, batch_id, client_batch):
      
      client = self._datastore_client
      batch_key = client.key(self._entity_kind_batches, batch_id)
      for img_id, img in iteritems(self._data[batch_id]['images']):
        img_entity = client.entity(
            client.key(self._entity_kind_images, img_id, parent=batch_key))
        for k, v in iteritems(img):
          img_entity[k] = v
        client_batch.put(img_entity)
docs: Helper method to write images from single batch into datastore.