Saves file with target class for given dataset batch.

    Args:
      filename: output filename
      image_batches: instance of ImageBatchesBase with dataset batches
      batch_id: dataset batch ID

def save_target_classes_for_batch(self,
                                    filename,
                                    image_batches,
                                    batch_id):
    """Saves file with target class for given dataset batch.

    Args:
      filename: output filename
      image_batches: instance of ImageBatchesBase with dataset batches
      batch_id: dataset batch ID
    """
    images = image_batches.data[batch_id]['images']
    with open(filename, 'w') as f:
      for image_id, image_val in iteritems(images):
        target_class = self.get_target_class(image_val['dataset_image_id'])
        f.write('{0}.png,{1}\n'.format(image_id, target_class))