code: def _transpose_dict_list(dict_list):
    
    # 1. Unstack numpy arrays into list
    dict_list = utils.map_nested(np_to_list, dict_list, dict_only=True)
  
    # 2. Extract the sequence length (and ensure the length is constant for all
    # elements)
    length = {'value': None}  # dict because `nonlocal` is Python3 only
    def update_length(elem):
      if length['value'] is None:
        length['value'] = len(elem)
      elif length['value'] != len(elem):
        raise ValueError(
            'The length of all elements of one sequence should be the same. '
            'Got {} != {}'.format(length['value'], len(elem)))
      return elem
    utils.map_nested(update_length, dict_list, dict_only=True)
  
    # 3. Extract each individual elements
    return [
        utils.map_nested(lambda elem: elem[i], dict_list, dict_only=True)   # pylint: disable=cell-var-from-loop
        for i in range(length['value'])
    ]
docs: Transpose a nested dict[list] into a list[nested dict].