func (connector *SIRIEstimatedTimetableSubscriptionBroadcaster) checkLines(ett *sxml.XMLEstimatedTimetableSubscriptionRequestEntry) (resources []*SubscribedResource, lineIds []string) {
    // check for subscription to all lines
    if len(ett.Lines()) == 0 {
        var lv []string
        //find all lines corresponding to the remoteCodeSpace