code: public static <E extends Enum<E>> StreamableEnumSet<E> of (E first, E... rest)
      {
          StreamableEnumSet<E> set = new StreamableEnumSet<E>(first.getDeclaringClass());
          set.add(first);
          for (E e : rest) {
              set.add(e);
          }
          return set;
      }
docs: Creates a set consisting of the specified elements.