What String to use in writemode update

My goal is to use SwiftyDropbox in my Swift iOS app to save the user's data and keep it synced between devices. I did this successfully by first deleting the existing file and then writing the updated file, but I would like to use the writemode update instead as that seems safer and better. The one thing I can't figure out is what String to use in the call mode: .update(String). I tried using the same string as the path and that resulted in an error.

I hope this isn't a dumb question, but I've spent the last hour scouring google, the documention, and this forum and I can't seem to find this answer.

Thank you!

let encodedCompleteLibrary = try? JSONEncoder().encode(completeLibrary)
        
        if _inDropboxSyncMode, let client = DropboxClientsManager.authorizedClient {
            if let fileData = encodedCompleteLibrary {
                let pathString: String = UserDefaultsKeys.dropboxFolderName + UserDefaultsKeys.completeLibraryFilename
                client.files.upload(path: pathString, mode: .update(?????), autorename: false, mute: false, input: fileData)
                .response { response, error in
                    if let response = response {
                        self._inOfflineMode = false
                        print(response)
                    } else if let error = error {
                        self._inOfflineMode = true
                        print(error)
                    }
                }
            }