How to use the htmlparser2.Stream function in htmlparser2

function discover(options, cb) {
    let discovered = [],
        contentType = '',
        errored = false

    let req = this._request = request(options),
        parser = this._parser = new htmlparser.Stream();

    req.on('error', onEnd);
    req.on('abort', function() {
        req.removeAllListeners();
        req.destroy();
    });
    req.on('response', function(response) {
        if (response.statusCode !== 200) {
            var err = new Error(req.httpModule.STATUS_CODES[response.statusCode] || 'Unknown HTTP response');
            err.code = response.statusCode;
            return onEnd(err);
        }

        if (response.headers['content-type']) {
            contentType = parseHttpHeader(response.headers['content-type'])[0];
        }