private void NavigationPopCallback(MessageBus bus, NavigationPopInfo navigationPopInfo)
 {
     if (navigationPopInfo == null)
     {
         throw new ArgumentNullException(nameof(navigationPopInfo));
     }
     Pop(navigationPopInfo);
 }
        private void Pop(NavigationPopInfo popInfo)
        {
            switch (popInfo.Mode)
            {
            case NavigationMode.Normal:
                NormalPop(popInfo.OnCompletedTask);
                break;

            case NavigationMode.Modal:
                ModalPop(popInfo.OnCompletedTask);
                break;

            case NavigationMode.Custom:
                CustomPop(popInfo.OnCompletedTask);
                break;

            default:
                throw new NotImplementedException();
            }
        }