/**
  * Returns parent for this make (or itself if it is already a parent)
  * @param DBmodel $model
  * @return type Parent
  */
 function get_parent_model(DBModel $model)
 {
     $parent = null;
     if ($model != null && $model->parentmodelid > 0) {
         $parent = DBModel::find_by_modelid($model->parentmodelid);
     } else {
         $parent = $model;
     }
     return $parent != null ? $parent : new DBModel(array('modelid' => 0, 'modelname' => '', 'parentmodelid' => 0));
 }