public Parser sync() {
        if (syncParser == null) {
           FutureParser future = scoped("sync");
           syncParser = future;
           future.setParser(
               sequence(
                   choice(
                       token("SYNCHRONIZED"),
                       token("SYNC")
                   ),
                   optional(
                       choice(
                           token("LEFT"),
                           token("RIGHT")
                       )
                   )
               )
           );
        }

        return syncParser;
    }