code: def move_inside(self, parent_id):
            # noqa
          session = Session.object_session(self)
          self.parent_id = parent_id
          self.mptt_move_inside = parent_id
          session.add(self)
docs: Moving one node of tree inside another
  
          For example see:
  
          * :mod:`sqlalchemy_mptt.tests.cases.move_node.test_move_inside_function`
          * :mod:`sqlalchemy_mptt.tests.cases.move_node.test_move_inside_to_the_same_parent_function`