input: Write a function to swap the values of two variables. Return the new values of the variables as a tuple.
  def swap_variables(x, y):
      x, y = y, x
      return (x, y)
  
  assert swap_variables(5, 10)==(10, 5)
  assert swap_variables(15, 20)==(20, 15)
  assert swap_variables("a", "b")==("b", "a")
  assert swap_variables(True, False)==(False, True)
  assert swap_variables([1, 2], [3, 4])==([3, 4], [1, 2])
output: def swap_variables(x, y):
      x, y = y, x
      return (x, y)