code: def watch(self, tube):
          
          with self._sock_ctx() as socket:
              self.desired_watchlist.add(tube)
              if tube not in self._watchlist:
                  self._send_message('watch {0}'.format(tube), socket)
                  self._receive_id(socket)
                  self._watchlist.add(tube)
                  if self.initial_watch:
                      if tube != 'default':
                          self.ignore('default')
                      self.initial_watch = False
docs: Add the given tube to the watchlist.
  
          :param tube: Name of the tube to add to the watchlist
  
          Note: Initially, all connections are watching a tube named "default". If
          you manually call :func:`watch()`, we will un-watch the "default" tube.
          To keep it in your list, first call :func:`watch()` with the other tubes, then
          call :func:`watch()` with "default".