docs: def revoke(self, cert_id, reason=''):
          """
          Revoke a certificate.
  
          :param int cert_id: The certificate ID
          :param str reason: Reason for revocation (up to 256 characters), can be blank: ''
          :return: The result of the operation, 'Successful' on success
          :rtype: dict
          """
          result = self.client.service.revoke(authData=self.auth, id=cert_id, reason=reason)
  
          if result == 0:
              return jsend.success()
          else:
              return self._create_error(result)