input: Write a function to swap the values of two variables x and y and return the swapped values as a tuple.
  def swap_variables(x, y):
      return y, x
  assert swap_variables(5, 10)==(10, 5)
  assert swap_variables(100, 200)==(200, 100)
  assert swap_variables("a", "b")==("b", "a")
  assert swap_variables(0, 0)==(0, 0)
  assert swap_variables(None, None)==(None, None)
output: def swap_variables(x, y):
      return y, x