Assets/Demos/TextMeshPro Support/ImportSample.cs(9,6): error CS0246: The type or namespace name 'MenuItemAttribute' could not be found (are you missing a using directive or an assembly reference?)

Assets/Demos/TextMeshPro Support/ImportSample.cs(9,6): error CS0246: The type or namespace name 'MenuItem' could not be found (are you missing a using directive or an assembly reference?)

Assets/Demos/TextMeshPro Support/ImportSample.cs(15,6): error CS0246: The type or namespace name 'MenuItemAttribute' could not be found (are you missing a using directive or an assembly reference?)

Assets/Demos/TextMeshPro Support/ImportSample.cs(15,6): error CS0246: The type or namespace name 'MenuItem' could not be found (are you missing a using directive or an assembly reference?)

Assets/Demos/TextMeshPro Support/ImportSample.cs(21,6): error CS0246: The type or namespace name 'InitializeOnLoadMethodAttribute' could not be found (are you missing a using directive or an assembly reference?)

Assets/Demos/TextMeshPro Support/ImportSample.cs(21,6): error CS0246: The type or namespace name 'InitializeOnLoadMethod' could not be found (are you missing a using directive or an assembly reference?)

Error building Player because scripts had compiler errors