public override void UnregisterAdapterDataObserver(global::Android.Support.V7.Widget.RecyclerView.AdapterDataObserver observer)
 {
     if (_observers == null || !_observers.Remove(observer))
     {
         base.UnregisterAdapterDataObserver(observer);
     }
 }
 public override void RegisterAdapterDataObserver(global::Android.Support.V7.Widget.RecyclerView.AdapterDataObserver observer)
 {
     if (_recyclerView == null)
     {
         if (_observers == null)
         {
             _observers = new List <global::Android.Support.V7.Widget.RecyclerView.AdapterDataObserver>();
         }
         _observers.Add(observer);
     }
     else
     {
         base.RegisterAdapterDataObserver(observer);
     }
 }