input: Write a function to swap the values of two variables. The function should accept two variables as input and return the swapped values. If either of the variables is empty, the function should return the original values.
  
  assert swap_values(5, 10)==(10, 5)
  assert swap_values(10, 5)==(5, 10)
  assert swap_values(0, 0)==(0, 0)
  assert swap_values(None, 5)==(None, 5)
  assert swap_values(5, None)==(5, None)
  assert swap_values(None, None)==(None, None)
output: def swap_values(a, b):
      if a is None or b is None:
          return a, b
      return b, a