public static function delete_comments_topic_module($module_id, $id_in_module)
 {
     $id_topic = CommentsTopicDAO::get_id_topic_module($module_id, $id_in_module);
     CommentsDAO::delete_comments_by_topic($id_topic);
     CommentsTopicDAO::delete_topic_module($module_id, $id_in_module);
     self::regenerate_cache();
 }