final Map<String, Object> source = new LinkedHashMap<>();
        source.put("title", "Test");
        source.put("content", "Body");
        source.put("cache", "cached");
        source.put("segment", "seg1");
        source.put("host", "example.com");

        final Set<String> excludeFields = Set.of("cache", "segment");
        final String html = new HtmlIndexExportFormatter().format(source, excludeFields);

   *
   * <p>Results are undefined if {@code set1} and {@code set2} are sets based on different
   * equivalence relations, for example if {@code set1} is a {@link HashSet} and {@code set2} is a
   * {@link TreeSet} or the {@link Map#keySet} of an {@code IdentityHashMap}.
   */
  public static <E extends @Nullable Object> SetView<E> difference(Set<E> set1, Set<?> set2) {
    checkNotNull(set1, "set1");

   */
  public static <E extends @Nullable Object> SetView<E> union(
      Set<? extends E> set1, Set<? extends E> set2) {
    checkNotNull(set1, "set1");
    checkNotNull(set2, "set2");

    return new SetView<E>() {
      @Override
      public int size() {
        int size = set1.size();
        for (E e : set2) {
          if (!set1.contains(e)) {
            size++;
          }
        }
        return size;

				"application/x-appleworks",
				"application/x-archive",
				"application/x-arj",
				"application/x-authorware-bin",
				"application/x-authorware-map",
				"application/x-authorware-seg",
				"application/x-bcpio",
				"application/x-berkeley-db",
				"application/x-bibtex-text-file",
				"application/x-bittorrent",
				"application/x-bplist",
				"application/x-bzip",
				"application/x-bzip2",