What is the correct way to write a doctest?
def sum(a, b): """ sum(4, 3) 7 sum(-4, 5) 1 """ return a + b
def sum(a, b): """ >>> sum(4, 3) 7 >>> sum(-4, 5) 1 """ return a + b
def sum(a, b): """ # >>> sum(4, 3)