extension String {
var htmlToAttributedString: NSAttributedString? {
    guard let data = data(using: .utf8) else { return nil }
    do {
        return try NSAttributedString(data: data,options: [NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType,NSCharacterEncodingDocumentAttribute: String.Encoding.utf8.rawValue],documentAttributes: nil)
    } catch let error as NSError {
        print(error.localizedDescription)
        return  nil
    }
}
var html2String: String {
    return htmlToAttributedString?.string ?? ""
}

我收到以下3个相同的错误

Use of unresolved identifier ‘NSDocumentTypeDocumentAttribute’

Use of unresolved identifier ‘NSHTMLTextDocumentType’

Use of unresolved identifier ‘NSCharacterEncodingDocumentAttribute’

我假设我犯了一个错误的语法导致3相同的错误但我无法看到扩展需要什么？

谢谢