func openDocument(url: URL) async -> String {
   let newDocument = MyDocument(fileURL: url)
   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(url: URL, content: String) async {
   let newDocument = MyDocument(fileURL: url)
   
   if let data = content.data(using: .utf8) {
      newDocument.fileContent = data
      let _ = await newDocument.save(to: url, for: .forOverwriting)
      await newDocument.close()
   }
}