/**
  * Suppression de document / modèle
  * 
  * @return string
  */
 function delete()
 {
     $this->completeField("content_id");
     $this->loadContent(false);
     $this->loadRefsFiles();
     // Remove PDF preview
     foreach ($this->_ref_files as $_file) {
         $_file->delete();
     }
     if ($msg = parent::delete()) {
         return $msg;
     }
     // Remove content
     return $this->_ref_content->delete();
 }