code: def watchlist(self, tubes):
          
          tubes = set(tubes)
          for tube in tubes - self._watchlist:
              self.watch(tube)
          for tube in self._watchlist - tubes:
              self.ignore(tube)
docs: Set the watchlist to the given tubes
  
          :param tubes: A list of tubes to watch
  
          Automatically un-watches any tubes that are not on the target list