code: func (media *FeedMedia) ID() string {
  	switch s := media.NextID.(type) {
  	case string:
  		return s
  	case int64:
  		return strconv.FormatInt(s, 10)
  	case json.Number:
  		return string(s)
  	}
  	return ""
  }
docs: // ID returns media id.