@Override
    public void clear() {
        map.clear();
    }
@Test
    public void testClear() {
        ExtendedSet<TestValue> set = new ExtendedSet<>(Maps.newConcurrentMap());
        TestValue val = new TestValue("foo", 1);
        assertTrue(set.add(val));
        assertTrue(set.contains(val));
        set.clear();
        assertFalse(set.contains(val));
    }