input: Write a function to calculate the average of a list of positive integers and output the result. The function should return the average as a float or an appropriate message if the list is empty.
  assert average_positive_integers([1, 5, 6, 7, 8])==5.4
  assert average_positive_integers([])=='The list is empty'
  assert average_positive_integers([2, 4, 6, 8])==5.0
  assert average_positive_integers([10])==10.0
  assert average_positive_integers([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])==5.5
output: def average_positive_integers(lst):
      if not lst:
          return 'The list is empty'
      return sum(lst) / len(lst)