docs: def percentage(value: str) -> float:
      """
      ``argparse`` argument type that checks that its value is a percentage (in
      the sense of a float in the range [0, 100]).
      """
      try:
          fvalue = float(value)
          assert 0 <= fvalue <= 100
      except (AssertionError, TypeError, ValueError):
          raise ArgumentTypeError(
              "{!r} is an invalid percentage value".format(value))
      return fvalue