def METHOD_NAME(self, instance):
    if not self.is_active(instance.data):
        return
    if not cmds.pluginInfo("mtoa", query=True, loaded=True):
        # Arnold attributes only exist if plug-in is loaded
        return
    invalid = self.get_invalid_attributes(instance, compute=True)
    if invalid:
        raise PublishValidationError(
            "Non-default Arnold attributes found in instance:"
            " {0}".format(invalid)
        )