input: Write a python function to sort an array in descending order.
  assert sort_array([3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5])==[9, 6, 5, 5, 5, 4, 3, 3, 2, 1, 1]
  assert sort_array([10, 20, 30, 40, 50])==[50, 40, 30, 20, 10]
  assert sort_array([7, 3, 5, 2, 6, 1, 4])==[7, 6, 5, 4, 3, 2, 1]
output: def sort_array(arr):
      return sorted(arr, reverse=True)