}

    @Override
    public Iterator<E> descendingIterator() {
      return Iterators.filter(unfiltered().descendingIterator(), predicate);
    }

    @Override
    @ParametricNullness
    public E last() {
      return Iterators.find(unfiltered().descendingIterator(), predicate);
    }

    @Override
    public NavigableSet<E> subSet(