/**
  *    get_all_event_tickets
  *
  * @access    protected
  * @param \EE_Event $event
  * @return bool
  */
 protected static function has_tickets_in_cart($event = null)
 {
     if (!$event instanceof EE_Event) {
         return false;
     }
     EED_Multi_Event_Registration::load_classes();
     $event_tickets = EED_Multi_Event_Registration::get_all_event_tickets($event);
     $tickets_in_cart = EE_Registry::instance()->CART->get_tickets();
     foreach ($tickets_in_cart as $ticket_in_cart) {
         if ($ticket_in_cart instanceof EE_Line_Item && $ticket_in_cart->OBJ_type() == 'Ticket' && isset($event_tickets[$ticket_in_cart->OBJ_ID()])) {
             return true;
         }
     }
     return false;
 }