Book(String name, ArdProto proto, {bool debug: false, Display display, int pageKnobId})

Source 

Book(this.name, ArdProto proto,
    {bool debug: false, Display display, this.pageKnobId})
    : this.debug = debug,
      this.proto = proto,
      _pages = <Page>[],
      _display = display ?? new Display(proto),
      _displayNone = new DisplayNone(proto, debug: debug) {
  proto.onAction.listen(_onKnob);
}