input: Write a python function to sort a list of numbers in descending order.
  assert sort_descending([2, 4, 1, 6, 5])==[6, 5, 4, 2, 1]
  assert sort_descending([10, 3, 22, 5])==[22, 10, 5, 3]
  assert sort_descending([7, 7, 7, 7])==[7, 7, 7, 7]
output: def sort_descending(lst):
      return sorted(lst, reverse=True)