code: def unload(self):
          
          self.is_loaded = False
          for evt in self._event_cache:
              self.context.unregister(
                  evt['event'], evt['callback'], evt['selector'])
          self._event_cache = {}
docs: Overridable method called when a view is unloaded (either on view change or on application shutdown).
          Handles by default the unregistering of all event handlers previously registered by
          the view.