code: def set_model(self, m):
          
          self._model = m
          self.new_root.emit(QtCore.QModelIndex())
          self.model_changed(m)
docs: Set the model for the level
  
          :param m: the model that the level should use
          :type m: QtCore.QAbstractItemModel
          :returns: None
          :rtype: None
          :raises: None