public Parser conditionalRelationOP() {
        if (conditionalRelationOPParser == null) {
           FutureParser future = scoped("conditionalRelationOP");
           conditionalRelationOPParser = future;
           future.setParser(
               choice(
                   token("AND"),
                   token("OR")
               )
           );
        }

        return conditionalRelationOPParser;
    }