input: Write a function to swap the values of two variables. The function should take two variables as input and swap their values. After swapping, print the values of the variables.
  assert swap_values(5, 10)=="x: 10\ny: 5"
  assert swap_values(15, 20)=="x: 20\ny: 15"
  assert swap_values("a", "b")=="x: b\ny: a"
  assert swap_values(True, False)=="x: False\ny: True"
output: def swap_values(x, y):
      x, y = y, x
      return f"x: {x}\ny: {y}"