public Tuple2<T1, T0> swap() {
        return new Tuple2<T1, T0>(f1, f0);
    }
@Test
    void testSwapValues() {
        Tuple2<String, Integer> toSwap = new Tuple2<>("Test case", 25);
        Tuple2<Integer, String> swapped = toSwap.swap();

        assertThat(toSwap.f1).isEqualTo(swapped.f0);

        assertThat(toSwap.f0).isEqualTo(swapped.f1);
    }