@Override
    public boolean contains(Object o) {
        checkNotNull(o, "The argument cannot be null");
        return items.contains(serializer.encode(o));
    }
@Test
    public void testContains() throws Exception {
        //Test contains
        assertFalse("The set should not contain anything", set.contains(1));
        fillSet(10, this.set);
        for (int i = 0; i < 10; i++) {
            assertTrue("The set should contain all values 0-9.", set.contains(i));
        }
    }