Return correct subdirectory of input base dir for artifacts corresponding to input rev reg id.

        :param base_dir: base directory for tails files, thereafter split by cred def id
        :param rr_id: rev reg id

def dir(base_dir: str, rr_id: str) -> str:
        """
        Return correct subdirectory of input base dir for artifacts corresponding to input rev reg id.

        :param base_dir: base directory for tails files, thereafter split by cred def id
        :param rr_id: rev reg id
        """

        return join(base_dir, rev_reg_id2cred_def_id(rr_id))