input: Write a function to add two numbers together and print the result.
  def add(a, b):
      sum = a + b
      print(sum)
  
  assert add(5, 7) == None
  assert add(3, 4) == None
  assert add(10, 0) == None
  assert add(-1, 5) == None
  assert add(0, 0) == None
output: def add(a, b):
      sum = a + b
      print(sum)