code: def _configuration(self, kwargs, config_item):
          
          if 'notification_configuration' not in config_item:
              if 'notification_type' not in kwargs:
                  return
              nc = kwargs['notification_configuration'] = {}
              for field in Resource.configuration[kwargs['notification_type']]:
                  if field not in config_item:
                      raise exc.TowerCLIError('Required config field %s not'
                                              ' provided.' % field)
                  else:
                      nc[field] = config_item[field]
          else:
              kwargs['notification_configuration'] = \
                      config_item['notification_configuration']
docs: Combine configuration-related keyworded arguments into
          notification_configuration.