FilteredSet<E> filtered = (FilteredSet<E>) unfiltered;
      Predicate<E> combinedPredicate = Predicates.and(filtered.predicate, predicate);
      return new FilteredNavigableSet<>((NavigableSet<E>) filtered.unfiltered, combinedPredicate);
    }

    return new FilteredNavigableSet<>(checkNotNull(unfiltered), checkNotNull(predicate));
  }

  private static class FilteredSet<E extends @Nullable Object> extends FilteredCollection<E>