shading_nodes.py

    for cls in classes:
        register_class(cls)


def unregister():
    # from bpy.utils import unregister_class

    for cls in reversed(classes):
        unregister_class(cls)
    nodeitems_utils.unregister_node_categories("POVRAYNODES")
    bpy.types.NODE_HT_header.remove(menu_func_nodes)