input: Write a python function to calculate the average of all elements in a list.
  assert averageList([1, 2, 3, 4]) == 2.5
  assert averageList([10, 20, 30, 40, 50]) == 30
  assert averageList([5, 15, 25, 35, 45, 55]) == 30
output: def averageList(lst):
      return sum(lst) / len(lst)