code: func (s *MgetService) Source() (interface{}, error) {
  	source := make(map[string]interface{})
  	items := make([]interface{}, len(s.items))
  	for i, item := range s.items {
  		src, err := item.Source()
  		if err != nil {
  			return nil, err
  		}
  		items[i] = src
  	}
  	source["docs"] = items
  	return source, nil
  }
docs: // Source returns the request body, which will be serialized into JSON.