@Nonnull
    public static <T> AggregateOperation1<T, PriorityQueue<T>, List<T>> bottomN(
            int n, @Nonnull ComparatorEx<? super T> comparator
    ) {
        return topN(n, comparator.reversed());
    }
@Test
    public void when_bottomN() {
        AggregateOperationsTest.validateOpWithoutDeduct(bottomN(2, naturalOrder()),
                ArrayList::new,
                Arrays.asList(7, 1, 5, 3),
                Arrays.asList(8, 6, 2, 4),
                Arrays.asList(3, 1),
                Arrays.asList(2, 1),
                Arrays.asList(1, 2)
        );
    }