Prefab Brush problem

HI everyone! I get these errors when I try to build my application, I’m using the “PrefabBrush.cs” script from the 2d-extras-master pack (GitHub - Unity-Technologies/2d-techdemos: Tech Demos for Unity 2D Features). Please help me:

Assets\Brushes\PrefabBrush.cs(10,32): error CS0246: The type or namespace name ‘GridBrush’ could not be found (are you missing a using directive or an assembly reference?)

Assets\Brushes\PrefabBrush.cs(49,30): error CS0115: ‘PrefabBrush.Erase(GridLayout, GameObject, Vector3Int)’: no suitable method found to override

Assets\Brushes\PrefabBrush.cs(93,17): error CS0246: The type or namespace name ‘SerializedObject’ could not be found (are you missing a using directive or an assembly reference?)

and more…

Delete your prefab brush objects and script but do some backup. After that build your app. It works for me. I just backup again what I delete.