sum_two sample solution parameter

For the sum_two_challenge notebook (link), the Solution class template only takes one parameter:

class Solution(object):

    def sum_two(self, val):
        # TODO: Implement me
        pass

That should change to two parameters:

class Solution(object):

    def sum_two(self, a, b):
        # TODO: Implement me
        pass

Otherwise a TypeError is raised with the message:

TypeError: sum_two() takes 2 positional arguments but 3 were given