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)
  add(10,3)
  add(0,0)
  add(-5,7)
  assert add(5, 7) == 12
  assert add(10, 3) == 13
  assert add(0, 0) == 0
  assert add(-5, 7) == 2
output: def add(a, b):
      sum = a + b
      print(sum)