import tensorflow as tf

    if isinstance(data_sources, (list, tuple)):
      data_files = []
      for source in data_sources:
        data_files += self.get_data_files(source)
    else:
      if '*' in data_sources or '?' in data_sources or '[' in data_sources:
        data_files = tf.gfile.Glob(data_sources)
      else:
        data_files = [data_sources]
    if not data_files:
      raise ValueError('No data files found in %s' % (data_sources,))
    return data_files
