}
    return new Itr<Entry<K, V>>() {
      @Override
      Entry<K, V> getOutput(int entry) {
        return new MapEntry(entry);
      }
    };
  }

  final class MapEntry extends AbstractMapEntry<K, V> {
    @ParametricNullness private final K key;

    private int lastKnownIndex;

    MapEntry(int index) {
      this.key = key(index);
      this.lastKnownIndex = index;
    }

   */
  static <K extends @Nullable Object, V extends @Nullable Object> Entry<K, V> unmodifiableEntry(
      Entry<? extends K, ? extends V> entry) {
    checkNotNull(entry);
    return new AbstractMapEntry<K, V>() {
      @Override
      @ParametricNullness
      public K getKey() {
        return entry.getKey();
      }

      @Override
      @ParametricNullness

   */
  static <K extends @Nullable Object, V extends @Nullable Object> Entry<K, V> unmodifiableEntry(
      Entry<? extends K, ? extends V> entry) {
    checkNotNull(entry);
    return new AbstractMapEntry<K, V>() {
      @Override
      @ParametricNullness
      public K getKey() {
        return entry.getKey();
      }

      @Override
      @ParametricNullness