code: func (v *Entry) GetIconTooltipMarkup(iconPos EntryIconPosition) (string, error) {
  	c := C.gtk_entry_get_icon_tooltip_markup(v.native(),
  		C.GtkEntryIconPosition(iconPos))
  	if c == nil {
  		return "", nilPtrErr
  	}
  	return goString(c), nil
  }
docs: // GetIconTooltipMarkup() is a wrapper around
  // gtk_entry_get_icon_tooltip_markup().