code: def move_after(self, node_id):
            # noqa
          session = Session.object_session(self)
          self.parent_id = self.parent_id
          self.mptt_move_after = node_id
          session.add(self)
docs: Moving one node of tree after another
  
          For example see :mod:`sqlalchemy_mptt.tests.cases.move_node.test_move_after_function`