input: Write a python function to output two numbers in descending order.
  assert descending_order(5, 10) == (10, 5)
  assert descending_order(20, 15) == (20, 15)
  assert descending_order(7, 7) == (7, 7)
output: def descending_order(a, b):
      if a > b:
          return (a, b)
      else:
          return (b, a)