code: func HelloWorld(nextSlide func()) (title string, content tview.Primitive) {
  	// We use a text view because we want to capture keyboard input.
  	textView := tview.NewTextView().SetDoneFunc(func(key tcell.Key) {
  		nextSlide()
  	})
  	textView.SetBorder(true).SetTitle("Hello, world!")
  	return "Hello, world", Code(textView, 30, 10, helloWorld)
  }
docs: // HelloWorld shows a simple "Hello world" example.