code: def unwatch(self):
          
          if self.watchers is not None:
              unwatched = []
              for watcher in self.watchers:
                  watcher.inst.param.unwatch(watcher)
                  unwatched.append(watcher)
              self.watchers = [w for w in self.watchers if w not in unwatched]
docs: Get rid of any lingering watchers and remove from list