          *     trace(s.pop());
          *     //3
          * </pre>
+         * @internal mutable
          */
         public function pop():*
         {

         *     trace(c);
         *     //Stream{1, 2, 3}
         * </pre>
         */
        public function flatten():Stream
        {


        /**
         * @private
         * @internal immutable
         */
        override flash_proxy function hasProperty(name:*):Boolean
        {
