code: static Function<String, Fragment> fragment(final Object tag) {
      return new Function<String, Fragment>() {
        @Override public Fragment apply(String text) {
          return Tokens.fragment(text, tag);
        }
        @Override public String toString() {
          return String.valueOf(tag);
        }
      };
    }
docs: Returns a map that tokenizes the recognized character range to a
  {@link Tokens.Fragment} object tagged with {@code tag}.