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