code: def model(self):
          
          if self._model is None and self.parentItem is not None:
              self._model = self.parentItem.model
          return self._model
docs: Returns the ConfigTreeModel this item belongs to.
              If the model is None (not set), it will use and cache the parent's model.
              Therefore make sure that an ancestor node has a reference to the model! Typically by
              setting the model property of the invisible root item in the model constructor.