code: func (a *API) UpdateWorksheet(cfg *Worksheet) (*Worksheet, error) {
  	if cfg == nil {
  		return nil, fmt.Errorf("Invalid worksheet config [nil]")
  	}
  
  	worksheetCID := string(cfg.CID)
  
  	matched, err := regexp.MatchString(config.WorksheetCIDRegex, worksheetCID)
  	if err != nil {
  		return nil, err
  	}
  	if !matched {
  		return nil, fmt.Errorf("Invalid worksheet CID [%s]", worksheetCID)
  	}
  
  	jsonCfg, err := json.Marshal(cfg)
  	if err != nil {
  		return nil, err
  	}
  
  	if a.Debug {
  		a.Log.Printf("[DEBUG] update worksheet, sending JSON: %s", string(jsonCfg))
  	}
  
  	result, err := a.Put(worksheetCID, jsonCfg)
  	if err != nil {
  		return nil, err
  	}
  
  	worksheet := &Worksheet{}
  	if err := json.Unmarshal(result, worksheet); err != nil {
  		return nil, err
  	}
  
  	return worksheet, nil
  }
docs: // UpdateWorksheet updates passed worksheet.