public function clean_up_resources()
 {
     $subquery = 'SELECT resourceID FROM ' . PERCH_DB_PREFIX . 'resource_log WHERE appID=' . $this->db->pdb('content');
     $Resources = new PerchResources();
     $resources = $Resources->get_not_in_subquery('content', $subquery);
     if (PerchUtil::count($resources)) {
         foreach ($resources as $Resource) {
             if ($Resource->is_not_in_use()) {
                 $Resource->delete();
             }
         }
     }
     $Perch = Perch::fetch();
     $Perch->event('region.cleanup', $this);
 }