input: Write a function to sort a list in descending order.
  assert descendingSort([13, 11, 7, 4, 2]) == [13, 11, 7, 4, 2]
  assert descendingSort([5, 1, 8, 3, 2]) == [8, 5, 3, 2, 1]
  assert descendingSort([20, 10, 30, 5]) == [30, 20, 10, 5]
output: def descendingSort(arr):
      return sorted(arr, reverse=True)