docs: public static Set<SelectorName> nameSetFrom( SelectorName firstName,
                                                   SelectorName... names ) {
          if (firstName == null && (names == null || names.length == 0)) {
              return Collections.emptySet();
          }
          Set<SelectorName> result = new LinkedHashSet<SelectorName>();
          result.add(firstName);
          for (SelectorName name : names) {
              if (name != null) result.add(name);
          }
          return Collections.unmodifiableSet(result);
      }