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, 20)
  add(-3, 3)
  add(0, 0)
  add(-5, -7)
  
  Assert Example:
  assert add(5, 7) is None
  assert add(10, 20) is None
  assert add(-3, 3) is None
  assert add(0, 0) is None
  assert add(-5, -7) is None
output: def add(a, b):
      sum = a + b
      print(sum)