code: func (v *Container) SetFocusChain(focusableWidgets []IWidget) {
  	var list *glib.List
  	for _, w := range focusableWidgets {
  		data := uintptr(unsafe.Pointer(w.toWidget()))
  		list = list.Append(data)
  	}
  	glist := (*C.GList)(unsafe.Pointer(list))
  	C.gtk_container_set_focus_chain(v.native(), glist)
  }
docs: // SetFocusChain is a wrapper around gtk_container_set_focus_chain().