input: 
  def swap_variables(x: int, y: int) -> (int, int):
      """ Swap the values of two variables and return them.
      >>> swap_variables(5, 10)
      (10, 5)
      >>> swap_variables(0, -1)
      (-1, 0)
      """
  
output:     temp = x
      x = y
      y = temp
      return x, y