func writeTransitions(ts system.TransitionSystem, labelNumberer *system.LabelNumberer, transitionsFilename string) { serializer, ok := ts.(system.TransitionSerializer) if !ok { log.Fatal("Transition system does not implement transition serialization") } f, err := os.Create(transitionsFilename) common.ExitIfError("Cannot create transition file:", err) defer f.Close() err = labelNumberer.WriteLabelNumberer(f, serializer) common.ExitIfError("Cannot create label file:", err) }