return (ImmutableSet<Cell<R, C, V>>) super.cellSet();
  }

  @Override
  abstract ImmutableSet<Cell<R, C, V>> createCellSet();

  @Override
  final UnmodifiableIterator<Cell<R, C, V>> cellIterator() {
    throw new AssertionError("should never be called");
  }

  @Override
  public ImmutableCollection<V> values() {
    return (ImmutableCollection<V>) super.values();
  }

  @Override

   */
  @Override
  public Set<Cell<R, C, @Nullable V>> cellSet() {
    return super.cellSet();
  }

  @Override
  Iterator<Cell<R, C, @Nullable V>> cellIterator() {
    return new AbstractIndexedListIterator<Cell<R, C, @Nullable V>>(size()) {
      @Override
      protected Cell<R, C, @Nullable V> get(final int index) {
        return getCell(index);
      }
    };