Swift - CloudKit - Delete Subscriptions

See:https://www.hackingwithswift.com/read/33/8/delivering-notifications-with-cloudkit-push-messages-ckquerysubscription

 let database = CKContainer.default().publicCloudDatabase

    database.fetchAllSubscriptions { [unowned self] subscriptions, error in
        if error == nil {
            if let subscriptions = subscriptions {
                for subscription in subscriptions {
                    database.delete(withSubscriptionID: subscription.subscriptionID) { str, error in
                        if error != nil {
                            // do your error handling here!
                            print(error!.localizedDescription)
                        }
                    }
                }

                // more code to come!
            }
        } else {
            // do your error handling here!
            print(error!.localizedDescription)
        }
    }