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