code: def obbTree(self):
          
          if not hasattr(self, '_obbTree'):
              self._obbTree = vtk.vtkOBBTree()
              self._obbTree.SetDataSet(self)
              self._obbTree.BuildLocator()
  
          return self._obbTree
docs: obbTree is an object to generate oriented bounding box (OBB)
          trees. An oriented bounding box is a bounding box that does not
          necessarily line up along coordinate axes. The OBB tree is a
          hierarchical tree structure of such boxes, where deeper levels of OBB
          confine smaller regions of space.