input: Write a function to add two numbers together and print the result.
  
  def add(a, b):
      sum = a + b
      print(sum)
  
  add(5, 7)
  
  assert add(5, 7) == 12
  assert add(3, 8) == 11
  assert add(-2, 2) == 0
  assert add(0, 0) == 0
  assert add(10, -5) == 5
output: def add(a, b):
      sum = a + b
      print(sum)