}

    @Override
    @CheckForNull
    public E pollFirst() {
      return Iterables.removeFirstMatching(unfiltered(), predicate);
    }

    @Override
    @CheckForNull
    public E pollLast() {
      return Iterables.removeFirstMatching(unfiltered().descendingSet(), predicate);
    }

    @Override
    public NavigableSet<E> descendingSet() {

    }

    @Override
    @CheckForNull
    public Entry<K, V> pollFirstEntry() {
      return Iterables.removeFirstMatching(unfiltered.entrySet(), entryPredicate);
    }

    @Override
    @CheckForNull
    public Entry<K, V> pollLastEntry() {
      return Iterables.removeFirstMatching(unfiltered.descendingMap().entrySet(), entryPredicate);
    }

    @Override

    }

    @Override
    @CheckForNull
    public Entry<K, V> pollFirstEntry() {
      return Iterables.removeFirstMatching(unfiltered.entrySet(), entryPredicate);
    }

    @Override
    @CheckForNull
    public Entry<K, V> pollLastEntry() {
      return Iterables.removeFirstMatching(unfiltered.descendingMap().entrySet(), entryPredicate);
    }

    @Override