* this implementation.
   *
   * @since 7.0
   */
  protected int standardIndexOf(@Nullable Object element) {
    return Lists.indexOfImpl(this, element);
  }

  /**
   * A sensible default implementation of {@link #lastIndexOf}, in terms of {@link
   * #listIterator(int)}. If you override {@link #listIterator(int)}, you may wish to override