fixed bug in problem 2 tests

                "true", "false");

        }

        if (chosen.size() != 3) {

        if (chosen.empty()) {

            return failExample(T,

                "K4 example should return 3 vertices in the planar induced subgraph",

                "3", to_string(chosen.size()));

                "maxPlanarSubgraph(K4) should return a non-empty vertex set",

                "non-empty", "empty");

        }

    }