How to use the haraka-net-utils.ipv6_reverse function in haraka-net-utils

}
                // Reverse IP for lookup
                lookup = host.split(/\./).reverse().join('.');
            }
            if (net.isIPv6(host)) {
                if (/^(?:1|true|yes|enabled|on)$/i.test(lists[zone].not_ipv6_compatible) || /^(?:1|true|yes|enabled|on)$/i.test(lists[zone].no_ip_lookups)) {
                    results.add(plugin, {skip: `IP (${host}) not supported for ${zone}` });
                    continue;
                }
                // Skip any private IPs
                if (net_utils.is_private_ip(host)) {
                    results.add(plugin, {skip: 'private IP' });
                    continue;
                }
                // Reverse IP for lookup
                lookup = net_utils.ipv6_reverse(host);
            }
            // Handle zones that require host to be stripped to a domain boundary
            else if (/^(?:1|true|yes|enabled|on)$/i.test(lists[zone].strip_to_domain)) {
                lookup = (tlds.split_hostname(host, 3))[1];
            }
            // Anything else..
            else {
                lookup = host;
            }
            if (!lookup) continue;
            if (!queries[zone]) queries[zone] = {};
            if (Object.keys(queries[zone]).length > lists.main.max_uris_per_list) {
                connection.logwarn(plugin, `discarding lookup ${lookup} for zone ${zone} maximum query limit reached`);
                results.add(plugin, {skip: `max query limit for ${zone}` });
                continue;
            }

exports.lookup = function (lookup, zone, cb) {
    const self = this;

    if (!lookup || !zone) {
        return setImmediate(() => cb(new Error('missing data')));
    }

    if (this.enable_stats) { this.init_redis(); }

    // Reverse lookup if IPv4 address
    if (net.isIPv4(lookup)) {
        lookup = lookup.split('.').reverse().join('.');
    }
    else if (net.isIPv6(lookup)) {
        lookup = net_utils.ipv6_reverse(lookup);
    }

    let start;
    if (this.enable_stats) {
        start = new Date().getTime();
    }

    // Build the query, adding the root dot if missing
    let query = [lookup, zone].join('.');
    if (query[query.length - 1] !== '.') {
        query += '.';
    }
    this.logdebug('looking up: ' + query);
    // IS: IPv6 compatible (maybe; only if BL return IPv4 answers)
    dns.resolve(query, 'A', (err, a) => {
        self.stats_incr_zone(err, zone, start);  // Statistics