input: 
  def calculate_average(positive_integers: List[int]) -> float:
      """ Calculate the average of a list of positive integers.
      >>> calculate_average([1, 5, 6, 7, 8])
      5.4
      >>> calculate_average([4, 9, 10, 2, 7])
      6.4
      """
  
output:     if not positive_integers:
          return 0.0
      total_sum = sum(positive_integers)
      count = len(positive_integers)
      return total_sum / count