* #elementSet}. If you override {@link #elementSet}, you may wish to override {@link #removeAll}
   * to forward to this implementation.
   *
   * @since 7.0
   */
  @Override
  protected boolean standardRemoveAll(Collection<?> elementsToRemove) {
    return Multisets.removeAllImpl(this, elementsToRemove);
  }

  /**
   * A sensible definition of {@link #retainAll} in terms of the {@code retainAll} method of {@link