code: def _client(self, key_id):
          
          region_name = _region_from_key_id(key_id, self.default_region)
          self.add_regional_client(region_name)
          return self._regional_clients[region_name]
docs: Returns a Boto3 KMS client for the appropriate region.
  
          :param str key_id: KMS CMK ID