code: def drilldown_tree(self, session=None, json=False, json_fields=None):
          
          if not session:
              session = object_session(self)
          return self.get_tree(
              session,
              json=json,
              json_fields=json_fields,
              query=self._drilldown_query
          )
docs: This method generate a branch from a tree, begining with current
          node.
  
          For example:
  
              node7.drilldown_tree()
  
              .. code::
  
                  level           Nested sets example
                  1                    1(1)22       ---------------------
                          _______________|_________|_________            |
                         |               |         |         |           |
                  2    2(2)5           6(4)11      |      12(7)21        |
                         |               ^         |         ^           |
                  3    3(3)4       7(5)8   9(6)10  | 13(8)16   17(10)20  |
                                                   |    |          |     |
                  4                                | 14(9)15   18(11)19  |
                                                   |                     |
                                                    ---------------------
  
          Example in tests:
  
              * :mod:`sqlalchemy_mptt.tests.cases.get_tree.test_drilldown_tree`