code: def mr_dim_ind(self):
          
          mr_dim_ind = self._cube.mr_dim_ind
          if self._cube.ndim == 3:
              if isinstance(mr_dim_ind, int):
                  if mr_dim_ind == 0:
                      # If only the 0th dimension of a 3D is an MR, the sliced
                      # don't actuall have the MR... Thus return None.
                      return None
                  return mr_dim_ind - 1
              elif isinstance(mr_dim_ind, tuple):
                  # If MR dimension index is a tuple, that means that the cube
                  # (only a 3D one if it reached this path) has 2 MR dimensions.
                  # If any of those is 0 ind dimension we don't need to include
                  # in the slice dimension (because the slice doesn't see the tab
                  # that it's on). If it's 1st and 2nd dimension, then subtract 1
                  # from those, and present them as 0th and 1st dimension of the
                  # slice. This can happend e.g. in a CAT x MR x MR cube (which
                  # renders MR x MR slices).
                  mr_dim_ind = tuple(i - 1 for i in mr_dim_ind if i)
                  return mr_dim_ind if len(mr_dim_ind) > 1 else mr_dim_ind[0]
  
          return mr_dim_ind
docs: Get the correct index of the MR dimension in the cube slice.