[vtkusers] change image slices with keyboard

[José M. Rodriguez Bacallao]

how folks, this is my second post about the subject, right now I am
using the following pipeline:

vtkImageResliceMapper -> vtkImageSlice -> vtkRenderer ->
vtkRenderWindow -> vtkRenderWindowInteractor
                /\                            /\
                                                            /\
                 |  output                  |
                                                          |
 vtkGDCMImageReader    vtkImageProperty
                       vtkInteractorStyleImage
(SetInteractionModeToImageSlicing)

everything is looking ok, I can change the from one slice to another
using the Ctrl + Left Mouse Button, but, I need to this same thing
with the keyboard (Left/Right cursor keys) and need to know the
current displayed slice, question is how do I do that?, I now how to
capture keyboard events and know which key was pressed, I am using
python by the way.

PS: sorry for my English, it's not so good.