@Override
      @ParametricNullness
      public T next() {
        return iterator.next();
      }
    };
  }

  /**
   * Simply returns its argument.
   *
   * @deprecated no need to use this
   * @since 10.0
   */
  @Deprecated
  public static <T extends @Nullable Object> UnmodifiableIterator<T> unmodifiableIterator(
      UnmodifiableIterator<T> iterator) {
    return checkNotNull(iterator);