@Override
    public final Set<Entry<K, V>> entrySet() {
        return delegate.entrySet();
    }
@Test
    public void requireThatSingletonEntrySetIteratorNextThrowsIfInvokedMoreThanOnce() {
        LazyMap<String, String> map = newSingletonMap("foo", "bar");
        Iterator<Map.Entry<String, String>> it = map.entrySet().iterator();
        it.next();
        try {
            it.next();
            fail();
        } catch (NoSuchElementException e) {

        }
        try {
            it.next();
            fail();
        } catch (NoSuchElementException e) {

        }
    }