public Parser sign() {
        if (signParser == null) {
           FutureParser future = scoped("sign");
           signParser = future;
           future.setParser(
               sequence(
                   optional(
                       sequence(
                           token("SIGN"),
                           optional(
                               token("IS")
                           )
                       )
                   ),
                   choice(
                       token("LEADING"),
                       token("TRAILING")
                   ),
                   optional(
                       sequence(
                           token("SEPARATE"),
                           optional(
                               token("CHARACTER")
                           )
                       )
                   )
               )
           );
        }

        return signParser;
    }