input: Write a function to swap the values of two variables. The function should take two parameters, x and y, and return the swapped values.
  assert swap_variables(5, 10)==(10, 5)
  assert swap_variables(100, 200)==(200, 100)
  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):
      return y, x