Return list of revocation registry identifiers for which HolderProver has tails files.

        :return: list of revocation registry identifiers for which HolderProver has tails files

def rev_regs(self) -> list:
        """
        Return list of revocation registry identifiers for which HolderProver has tails files.

        :return: list of revocation registry identifiers for which HolderProver has tails files
        """

        LOGGER.debug('HolderProver.rev_regs >>>')

        rv = [basename(f) for f in Tails.links(self._dir_tails)]
        LOGGER.debug('HolderProver.rev_regs <<< %s', rv)
        return rv