def _batch_name(split_name, offset, dataset):
  """Returns the file name for a given batch.
  
  Args:
    split_name: "train"|"test"
    offset: batch index (0-indexed)
    dataset: "cifar10"|"cifar100"
  """
  if dataset == 'cifar10':
    if split_name == 'train':
      return 'data_batch_%d' % (offset + 1)  # 1-indexed.
    else:
      return 'test_batch'
  else:
    return split_name