def unregister():
ypup = get_user_preferences() # may be None
if ypup and not hasattr(ypup, 'show_experimental') or ypup.show_experimental:
bpy.utils.unregister_class(VIEW3D_PT_y_vcol_editor_ui)
if not is_greater_than_280():
bpy.utils.unregister_class(VIEW3D_PT_y_vcol_editor_tools)