Missing postNotification method in onesignal_flutter V5 IOS

Question

In flutter I am sending silent notification in my IOS app using onesignal, perviously I was using onesignal version 3 and in that there is a method postNotification which was used to display silent notification received in conditionally

override func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable : Any]) {
 OneSignal.postNotification(content,onSuccess: {
                     osResultSuccessBlock in debugPrint(osResultSuccessBlock.debugDescription)
                     dailyNotificationCount += 1;
                     UserDefaults.standard.set(dailyNotificationCount, forKey: "flutter.dailyNotificationsCount")
                 },
                                            onFailure: {
                     osFailureBlock in debugPrint(osFailureBlock.debugDescription)
                 })
}

now that I have upgraded my version of onesignal to 5.1 it not longer have this method.

I have searched but was unable to find any method similar to this in onesignal migration guide or its documentation.