code: func (subs *Subtitles) toTryUploadParams() (map[string]interface{}, error) {
  	subMap := map[string]interface{}{}
  	for i, s := range *subs {
  		key := "cd" + strconv.Itoa(i+1) // keys are cd1, cd2, ...
  		subMap[key] = s.toUploadParams()
  	}
  
  	return subMap, nil
  }
docs: // Serialize Subtitle to OSDB's XMLRPC params when trying to upload.