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

      class MapEntry extends AbstractMapEntry<K, V> {
        private BiEntry<K, V> delegate;

        MapEntry(BiEntry<K, V> entry) {
          this.delegate = entry;
        }

        @Override
        @ParametricNullness

   * null} even for a map which supposedly does not contain null elements, if the key is not present
   * when {@code getValue()} is called.
   */
  final class EntryForKey extends AbstractMapEntry<K, V> {
    @ParametricNullness final K key;
    int index;

    EntryForKey(int index) {
      // The cast is safe because we call forEntry only for indexes that contain entries.