+ def delete_extra(self, session, _id, db_content):
+ """
+ Deletes file system storage associated with the descriptor
+ :param session: contains "username", "admin", "force", "public", "project_id", "set_project"
+ :param _id: server internal id
+ :param db_content: The database content of the descriptor
+ :return: None if ok or raises EngineException with the problem
+ """