docs: async def revoke_cred(self, rr_id: str, cr_id) -> int:
          """
          Revoke credential that input revocation registry identifier and
          credential revocation identifier specify.
  
          Return (epoch seconds) time of revocation.
  
          Raise AbsentTails if no tails file is available for input revocation registry identifier.
          Raise WalletState for closed wallet.
          Raise BadRevocation if issuer cannot revoke specified credential for any other reason
          (e.g., did not issue it, already revoked it).
  
          :param rr_id: revocation registry identifier
          :param cr_id: credential revocation identifier
          :return: time of revocation, in epoch seconds
          """
  
          LOGGER.debug('Issuer.revoke_cred >>> rr_id: %s, cr_id: %s', rr_id, cr_id)
  
          if not self.wallet.handle:
              LOGGER.debug('Issuer.revoke_cred <!< Wallet %s is closed', self.name)
              raise WalletState('Wallet {} is closed'.format(self.name))
  
          if not ok_rev_reg_id(rr_id):
              LOGGER.debug('Issuer.revoke_cred <!< Bad rev reg id %s', rr_id)
              raise BadIdentifier('Bad rev reg id {}'.format(rr_id))
  
          tails_reader_handle = (await Tails(
              self.dir_tails,
              *rev_reg_id2cred_def_id_tag(rr_id)).open()).reader_handle
          try:
              rrdelta_json = await anoncreds.issuer_revoke_credential(
                  self.wallet.handle,
                  tails_reader_handle,
                  rr_id,
                  cr_id)
          except IndyError as x_indy:
              LOGGER.debug(
                  'Issuer.revoke_cred <!< Could not revoke revoc reg id %s, cred rev id %s: indy error code %s',
                  rr_id,
                  cr_id,
                  x_indy.error_code)
              raise BadRevocation(
                  'Could not revoke revoc reg id {}, cred rev id {}: indy error code {}'.format(
                      rr_id,
                      cr_id,
                      x_indy.error_code))
  
          rr_ent_req_json = await ledger.build_revoc_reg_entry_request(self.did, rr_id, 'CL_ACCUM', rrdelta_json)
          resp_json = await self._sign_submit(rr_ent_req_json)  # raises AbsentPool or ClosedPool if applicable
          resp = json.loads(resp_json)
  
          rv = self.pool.protocol.txn2epoch(resp)
          LOGGER.debug('Issuer.revoke_cred <<< %s', rv)
          return rv