public void add(Sequence value) {
        // TODO we can probably optimize this a bit
        for(long i=value.first; i<value.last+1; i++) {
            add(i);
        }
    }
@Test
    public void testIsEmpty() {
        SequenceSet set = new SequenceSet();
        assertTrue(set.isEmpty());
        set.add(1);
        assertFalse(set.isEmpty());
    }