@Override
    public boolean remove(Object o) {
        return map.remove(o) != null;
    }
@Test
    public void testRemove() {
        ExtendedSet<TestValue> set = new ExtendedSet<>(Maps.newConcurrentMap());
        TestValue val = new TestValue("foo", 1);
        assertTrue(set.add(val));
        TestValue nextval = new TestValue("goo", 2);
        assertTrue(set.add(nextval));
        assertTrue(set.remove(val));
        assertFalse(set.contains(val));
        assertTrue(set.remove(nextval));
        assertFalse(set.contains(nextval));
    }