Concat issue

ConnectableObservable<String> remoteUserIdObservable =
        mUserClient
                .login()
                .map(this::checkNonNull)
                .doOnNext(this::logIn)
                .map(UserModel::_id);
Observable<String> outputObservable =  Observable
        .concat(mSessionManager.getUserIdAsObservable(), remoteUserIdObservable);
        
public Observable<String> getUserIdAsObservable() {
return rxSharedPreferences
    .getString(USER_LOGIN_KEYS.LOGIN_USER_ID.toString())
    .asObservable();
}


@GET("/user")
Observable<UserModel> login();