input: Write a python function to sort a list of items in descending order.
  assert my_sort([4, 2, 9, 1]) == [9, 4, 2, 1]
  assert my_sort([10, 20, 5, 15]) == [20, 15, 10, 5]
  assert my_sort([3, 3, 2, 1]) == [3, 3, 2, 1]
output: def my_sort(items):
      return sorted(items, reverse=True)