public Parser blockContains() {
        if (blockContainsParser == null) {
           FutureParser future = scoped("blockContains");
           blockContainsParser = future;
           future.setParser(
               sequence(
                   token("BLOCK"),
                   optional(
                       token("CONTAINS")
                   ),
                   integer(),
                   optional(
                       sequence(
                           token("TO"),
                           integer()
                       )
                   ),
                   optional(
                       choice(
                           token("CHARACTERS"),
                           token("RECORDS")
                       )
                   )
               )
           );
        }

        return blockContainsParser;
    }