input: def average_of_list(positive_integers: List[int]) -> float:
      """ Calculate the average of a list of positive integers and output the result.
      >>> average_of_list([1, 5, 6, 7, 8])
      5.4
      >>> average_of_list([2, 4, 6, 8, 10])
      6.0
      """
output:     if not positive_integers:
          return 0.0
      return sum(positive_integers) / len(positive_integers)