(getAncestor() == null) ? this : getAncestor());
    }

    @Override
    public SortedSet<V> subSet(@ParametricNullness V fromElement, @ParametricNullness V toElement) {
      refreshIfEmpty();
      return new WrappedSortedSet(
          getKey(),
          getSortedSetDelegate().subSet(fromElement, toElement),
          (getAncestor() == null) ? this : getAncestor());
    }