def _reindex(self):
        """
        Index every sentence into a cluster
        """
        self._len2split_idx = {}
        last_split = -1
        for split_idx, split in enumerate(self._splits):
            self._len2split_idx.update(
                dict(list(zip(list(range(last_split + 1, split)), [split_idx] * (split - (last_split + 1))))))