code: def read_index(group, version='1.1'):
      
      if version == '0.1':
          return np.int64(group['index'][...])
      elif version == '1.0':
          return group['file_index'][...]
      else:
          return group['index'][...]
docs: Return the index stored in a h5features group.
  
      :param h5py.Group group: The group to read the index from.
      :param str version: The h5features version of the `group`.
      :return: a 1D numpy array of features indices.