How to use the haraka-net-utils.is_private_ipv4 function in haraka-net-utils

loc = loc[part];   // descend
                continue;
            }

            // last part, so assign the value
            loc[part] = val;
        }

        // Set is_private, is_local automatically when remote.ip is set
        if (prop_str === 'remote.ip') {
            this.set('remote.is_local', net_utils.is_local_ip(this.remote.ip));
            if (this.remote.is_local) {
                this.set('remote.is_private', true);
            }
            else {
                this.set('remote.is_private', net_utils.is_private_ipv4(this.remote.ip));
            }
        }

        // sunset 3.0.0
        if (prop_str === 'hello.verb') {
            this.greeting = val;
        }
        else if (prop_str === 'tls.enabled') {
            this.using_tls = val;
        }
        else if (prop_str === 'proxy.ip') {
            this.haproxy_ip = val;
        }
        else {
            const legacy_name = prop_str.split('.').join('_');
            this[legacy_name] = val;