code: func (subs *Subtitles) toUploadParams() (map[string]interface{}, error) {
  	langID := (*subs)[0].SubLanguageID
  	params := map[string]interface{}{}
  
  	params["baseinfo"] = map[string]string{
  		"sublanguageid": langID,
  		// FIXME add "idmovieimdb"
  	}
  
  	for i, s := range *subs {
  		key := "cd" + strconv.Itoa(i+1) // keys are cd1, cd2, ...
  		subParam := s.toUploadParams()
  		encoded, err := s.encodeFile()
  		if err != nil {
  			return nil, err
  		}
  		subParam["subcontent"] = encoded
  		params[key] = subParam
  	}
  
  	return params, nil
  }
docs: // Serialize Subtitle to OSDB's XMLRPC params when uploading.