code: def set_close_down_mode(self, mode, onerror = None):
          
          request.SetCloseDownMode(display = self.display,
                                   onerror = onerror,
                                   mode = mode)
docs: Control what will happen with the client's resources at
          connection close. The default is X.DestroyAll, the other values
          are X.RetainPermanent and X.RetainTemporary.