code: def update_callback(self, fd, handle, events):
          
          if self._mpoll is None:
              raise RuntimeError('Poller instance is closed')
          mpoll = self._mpoll.get(fd)
          if mpoll is None:
              raise ValueError('not watching fd {}'.format(fd))
          mpoll.update_callback(handle, events)
docs: Update the event mask associated with an existing callback.
  
          If you want to temporarily disable a callback then you can use this
          method with an *events* argument of ``0``. This is more efficient than
          removing the callback and adding it again later.