code: def scene_node(self):
          
          if self._scene_node is None:
              from .subscene import SubScene
              p = self.parent
              while True:
                  if isinstance(p, SubScene) or p is None:
                      self._scene_node = p
                      break
                  p = p.parent
              if self._scene_node is None:
                  self._scene_node = self
          return self._scene_node
docs: The first ancestor of this node that is a SubScene instance, or self
          if no such node exists.