如何在swift 3中将文本视图偏移为键盘的高度？

override func viewDidLoad() {
    super.viewDidLoad()
    
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillShow(_:)), name: UIResponder.keyboardWillShowNotification, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillHide(_:)), name: UIResponder.keyboardWillHideNotification, object: nil)
}

@objc func keyboardWillShow(_ notification: Notification) {
    if let keyboardSize = (notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue {
        let contentInsets = UIEdgeInsets(top: 0, left: 0, bottom: keyboardSize.height, right: 0)
        yourTextView.contentInset = contentInsets
        yourTextView.scrollIndicatorInsets = contentInsets
    }
}

@objc func keyboardWillHide(_ notification: Notification) {
    let contentInsets = UIEdgeInsets.zero
    yourTextView.contentInset = contentInsets
    yourTextView.scrollIndicatorInsets = contentInsets
}

deinit {
    NotificationCenter.default.removeObserver(self)
}