return Multisets.removeAllImpl(this, elementsToRemove);
  }

  @CanIgnoreReturnValue
  @Override
  public final boolean retainAll(Collection<?> elementsToRetain) {
    return Multisets.retainAllImpl(this, elementsToRetain);
  }

  @Override
  public abstract void clear();

  // Views

  @LazyInit private transient @Nullable Set<E> elementSet;

  @Override