code: def mr_dim_ind(self):
          
          # TODO: rename to `mr_dim_idxs` or better yet get rid of need for
          # this as it's really a cube internal characteristic.
          # TODO: Make this return a tuple in all cases, like (), (1,), or (0, 2).
          indices = tuple(
              idx
              for idx, d in enumerate(self.dimensions)
              if d.dimension_type == DT.MR_SUBVAR
          )
          if indices == ():
              return None
          if len(indices) == 1:
              return indices[0]
          return indices
docs: Return int, tuple of int, or None, representing MR indices.
  
          The return value represents the index of each multiple-response (MR)
          dimension in this cube. Return value is None if there are no MR
          dimensions, and int if there is one MR dimension, and a tuple of int
          when there are more than one. The index is the (zero-based) position
          of the MR dimensions in the _ApparentDimensions sequence returned by
          the :attr"`.dimensions` property.