Sorry, But i tested it like this: 
var connection = new Steam.SteamClient();
var client = new Steam.SteamUser(connection);
var manager = new TradeOfferManager({
   "steam": client,
   "domain": domain,
   "language": "en",
   "cancelTime": cancel_time,
   "pendingCancelTime": cancel_time
});
var community = new SteamCommunity();
var logOnOptions = {
   "account_name": login_username,
   "password": login_password,
   "two_factor_code": SteamTotp.getAuthCode(login_secret)
};
client.logOn(logOnOptions);and I am getting errors now:   
this._connection.send(Buffer.concat([header.toBuffer(), body]));
                  ^
TypeError: Cannot read property 'send' of undefined
Is anything different when I use 'steam' ? I just used 'steam-user' before