How to use the open-sml.SmlFile function in open-sml

SmlProtocol.prototype.handleMessage = function handleMessage(message) {
    message = message.toString('hex');
    var regMessage = message.match(regCompleteMsg);
    if (!regMessage || !regMessage[1]) {
        this.callUserCallback(new Error('Message ' + message + 'invalid'), null);
        return null;
    }

    var smlFile = new OpenSml.SmlFile();

    var idx = message.indexOf(regMessage[1]);
    if (this.options.debug === 2) this.options.logger('MSG IDX ' + idx);
    try {
        smlFile.parse(Buffer.from(regMessage[1], 'hex'));
    }
    catch (err) {
        smlFile = null;
        this.callUserCallback(new Error('Error while parsing SML message: ' + err + ': Message: ' + regMessage[1]), null);
        if (idx !== -1) {
            return Buffer.from(message.substr(idx+regMessage[1].length), 'hex');
        }
        return null;
    }

    if (this.options.debug === 2) this.options.logger('SML MESSAGE: ' + smlFile.toString());