Implement function q3b(string1, string2) so that it returns a list of the indices, in increasing order, at which string1 and string2 have identical characters. That is, index i should be in the returned list if the ith character of string1 and string2 are the same. For example, q3b("cba", "cb") should return [0, 1] and q3b("bbcz", "Bbxzf") should return [1, 3].