change blendMode in vtkResliceCursor

My environment is Python 3.7.0 and VTK 9.1.0
I am realizing my own MPR application with example. The following is the snapshot on the rendering window.

I know the class vtkResliceCursorWidget internally uses vtk vtkImageSlabReslice, so that it can change the thickness of slice. However, I want to use my own BlendMode (MIP, MEAN MIN or etc). I cannot find the specific way to get the internal object of vtkImageSlabReslice. Anyone can help to give some clues? Do I need to build up the whole wheel myself from the beginning of vtkImageResliceSlab?