code: def _nav_naxis(self, viewer, axis, direction, msg=True):
          
          image = viewer.get_image()
          if image is None:
              return
          mddata = image.get_mddata()
          if len(mddata.shape) < (axis + 1):
              # image dimensions < 3D
              return
  
          naxispath = list(image.naxispath)
          axis_lim = mddata.shape[axis]
          m = axis - 2
  
          idx = naxispath[m]
          if direction == 'down':
              idx = (idx + 1) % axis_lim
          else:
              idx = idx - 1
              if idx < 0:
                  idx = axis_lim - 1
  
          naxispath[m] = idx
          image.set_naxispath(naxispath)
docs: Interactively change the slice of the image in a data cube
          by scrolling.