Return a new cigar with cigar string where the last `n_seq_bases` are
        soft-masked unless they are already hard-masked.

def mask_right(self, n_seq_bases, mask="S"):
        """
        Return a new cigar with cigar string where the last `n_seq_bases` are
        soft-masked unless they are already hard-masked.
        """
        return Cigar(Cigar(self._reverse_cigar()).mask_left(n_seq_bases, mask)._reverse_cigar())