public function getColumnIdOfKanbanItem(Tracker_Artifact $artifact)
 {
     $row = $this->item_dao->getColumnIdOfKanbanItem($artifact->getTrackerId(), $artifact->getId())->getRow();
     if (!$row) {
         return null;
     }
     return (int) $row['bindvalue_id'];
 }
 public function count_closed_kanban_items()
 {
     return $this->kanban_item_dao->getKanbanArchiveItemIds($this->kanban->getTrackerId())->count();
 }