input: Write a function to swap the values of two variables without using a third variable. The function should take two parameters, x and y, and return the swapped values.
  
  assert swap(5, 10) == (10, 5)
  assert swap(0, -1) == (-1, 0)
  assert swap("a", "b") == ("b", "a")
  assert swap(1.5, 2.5) == (2.5, 1.5)
  assert swap(True, False) == (False, True)
output: def swap(x, y):
      x, y = y, x
      return x, y