input: Write a function named swap_variables that takes two variables x and y as input and swaps their values. The function should print the values of x and y before and after swapping. 
  assert swap_variables(5, 10) == None
  assert swap_variables(100, 200) == None
output: def swap_variables(x, y):
      print("Before swapping: x =", x, "y =", y)
      x, y = y, x
      print("After swapping: x =", x, "y =", y)