protected function set_file_delete_properties($file)
 {
     parent::set_file_delete_properties($file);
     if ($this->delete_url != null) {
         if (substr($this->delete_url, -1) != '/') {
             $this->delete_url .= '/';
         }
         $file->delete_url = $this->delete_url . rawurlencode($file->name);
     }
 }