*
   * @return collection of values
   */
  @Override
  public Collection<@Nullable V> values() {
    return super.values();
  }

  @Override
  Iterator<@Nullable V> valuesIterator() {
    return new AbstractIndexedListIterator<@Nullable V>(size()) {
      @Override
      @CheckForNull
      protected V get(int index) {
        return getValue(index);
      }
    };
  }