public static AuditActor system(@Nonnull NodeId nodeId) {
        return new AutoValue_AuditActor(URN_GRAYLOG_NODE + requireNonNull(nodeId, "nodeId must not be null").getNodeId());
    }
@Test(expected = NullPointerException.class)
    public void testNullSystem() {
        AuditActor.system(null);
    }