implements Iterator<T> {
  final Iterator<? extends F> backingIterator;

  TransformedIterator(Iterator<? extends F> backingIterator) {
    this.backingIterator = checkNotNull(backingIterator);
  }

  @ParametricNullness
  abstract T transform(@ParametricNullness F from);

  @Override
  public final boolean hasNext() {
    return backingIterator.hasNext();
  }

  @Override
  @ParametricNullness

  TransformedListIterator(ListIterator<? extends F> backingIterator) {
    super(backingIterator);
  }

  private ListIterator<? extends F> backingIterator() {
    return (ListIterator<? extends F>) backingIterator;
  }

  @Override
  public final boolean hasPrevious() {
    return backingIterator().hasPrevious();
  }

  @Override
  @ParametricNullness
  public final T previous() {

  TransformedListIterator(ListIterator<? extends F> backingIterator) {
    super(backingIterator);
  }

  private ListIterator<? extends F> backingIterator() {
    return (ListIterator<? extends F>) backingIterator;
  }

  @Override
  public final boolean hasPrevious() {
    return backingIterator().hasPrevious();
  }

  @Override
  @ParametricNullness
  public final T previous() {