The code available for download at : https://developer.apple.com/documentation/mapkit/mapkit_annotations/annotating_a_map_with_custom_data Does not work, line 18 of CustomAnnotationView.swift :  private let blurEffect = UIBlurEffect(style: .systemThickMaterial) returns with error that : Type 'UIBlurEffect.Style' has no member 'systemThickMaterial'