我遇到以下错误：

  

RuntimeError：字典在迭代过程中更改了大小

运行Matthew Scarpino的书中的代码示例时。不确定如何解决此问题。

// in the viewDidLoad()
        bannerView = GADBannerView(adSize: kGADAdSizeBanner)

        bannerView.adUnitID = "ca-app-pub-2217093431614134/7329876635"
        bannerView.rootViewController = self
        bannerView.load(GADRequest())

        bannerView.delegate = self

        addBannerViewToView(bannerView)

// function to add Banner ad to view
func addBannerViewToView(_ bannerView: GADBannerView) {
        bannerView.translatesAutoresizingMaskintoConstraints = false
        view.addSubview(bannerView)
        view.addConstraints(
        [NSLayoutConstraint(item: bannerView,attribute: .bottom,relatedBy: .equal,toItem: view.safeAreaLayoutGuide,multiplier: 1,constant: 0),NSLayoutConstraint(item: bannerView,attribute: .centerX,toItem: view,constant: 0)
        ])
    }

请帮助