code: func NewOptionsGroupSelectBlockElement(
  	optType string,
  	placeholder *TextBlockObject,
  	actionID string,
  	optGroups ...*OptionGroupBlockObject,
  ) *SelectBlockElement {
  	return &SelectBlockElement{
  		Type:         optType,
  		Placeholder:  placeholder,
  		ActionID:     actionID,
  		OptionGroups: optGroups,
  	}
  }
docs: // NewOptionsGroupSelectBlockElement returns a new instance of SelectBlockElement for use with
  // the Options object only.