* java.util.stream.Stream#filter}. This method is not being deprecated, but we gently encourage
   * you to migrate to streams.
   */
  // TODO(kevinb): how to omit that last sentence when building GWT javadoc?
  public static <E extends @Nullable Object> Set<E> filter(
      Set<E> unfiltered, Predicate<? super E> predicate) {
    if (unfiltered instanceof SortedSet) {
      return filter((SortedSet<E>) unfiltered, predicate);

            The classifier of the dependency. It is appended to
            the filename after the version. This allows:
            <ul>
            <li>referring to attached artifact, for example {@code sources} and {@code javadoc}:
            see <a href="../maven-core/artifact-handlers.html">default artifact handlers</a> for a list,</li>
            <li>distinguishing two artifacts
            that belong to the same POM but were built differently.