def enforce_integer(f):
    def wrapper(*args):
        assert all([isinstance(x, int) for x in args]), \
               "all arguments most be int"

        return f(*args)

    return wrapper

@enforce_integer
def integer_sum(*args):
    return sum(args)

integer_sum(1,2,3,4)
integer_sum(1,2,3.2,4)