Update following the RFC

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/Views/MaterialGraphView.cs

             Insert(0, new GridBackground());
 
             AddStyleSheetPath("Styles/MaterialGraph");
+
+            serializeCopyPasteData = SerializeCopyPasteDataImplementation;
+            canPasteSerializedData = CanPasteSerializedDataImplementation;
+            unserializeAndPaste = UnserializeAndPasteImplementation;
+            deleteSelection = DeleteSelectionImplementation;
         }
 
         public bool CanAddToNodeMenu(Type type)
             PropagateSelection();
         }
 
-        protected override string SerializeCopyPasteData(IEnumerable<GraphElement> elements)
+        string SerializeCopyPasteDataImplementation(IEnumerable<GraphElement> elements)
-        protected override bool CanPasteSerializedData(string serializedData)
+        bool CanPasteSerializedDataImplementation(string serializedData)
-        protected override void UnserializeAndPasteOperation(string operationName, string serializedData)
+        void UnserializeAndPasteImplementation(string operationName, string serializedData)
         {
             var mgp = GetPresenter<MaterialGraphPresenter>();
             mgp.graph.owner.RegisterCompleteObjectUndo(operationName);
 
-        protected override void DeleteSelectionOperation(string operationName)
+        void DeleteSelectionImplementation(string operationName, GraphView.AskUser askUser)
         {
             var mgp = GetPresenter<MaterialGraphPresenter>();
             mgp.graph.owner.RegisterCompleteObjectUndo(operationName);