def _last_index(self, s):
        self.set_index(max(0, self._find_one_after_last_labeled_index() - 1))
def sls(n, d):
            gg = te.reduce_axis((0, lengths[n]))
            indices_idx = length_offsets[n] + gg
            data_idx = indices[indices_idx]
            data_val = data[data_idx, d]
            return te.sum(data_val, axis=gg)