func openDocument() async -> String {
   let manager = FileManager.default
   if let fileURL = manager.url(forUbiquityContainerIdentifier: nil) {
      let documentURL = fileURL.appendingPathComponent("Documents/myfile.dat")
      let newDocument = MyDocument(fileURL: documentURL)
      let success = await newDocument.open()
      if success {
         if let data = newDocument.fileContent {
            let content = String(data: data, encoding: .utf8) ?? ""
            await newDocument.close()
            return content
         }
      }
   }
   return ""
}
func saveDocument(text: String) async {
   let manager = FileManager.default
   if let fileURL = manager.url(forUbiquityContainerIdentifier: nil) {
      let documentURL = fileURL.appendingPathComponent("Documents/myfile.dat")

      let newDocument = MyDocument(fileURL: documentURL)
      if let data = text.data(using: .utf8) {
         newDocument.fileContent = data
         let _ = await newDocument.save(to: documentURL, for: .forOverwriting)
      }
      await newDocument.close()
   }
}