docs: def gen_part_from_iterables(iterables: Iterable[Any],
                              part_index: int) -> Generator[Any, None, None]:
      r"""
      Yields the *n*\ th part of each thing in ``iterables``.
  
      Args:
          iterables: iterable of anything
          part_index: part index
  
      Yields:
          ``item[part_index] for item in iterable``
  
      """
      # RST: make part of word bold/italic:
      # https://stackoverflow.com/questions/12771480/part-of-a-word-bold-in-restructuredtext  # noqa
      for iterable in iterables:
          yield iterable[part_index]