public static void clean(
            Object func, ExecutionConfig.ClosureCleanerLevel level, boolean checkSerializable) {
        clean(func, level, checkSerializable, Collections.newSetFromMap(new IdentityHashMap<>()));
    }
@Test
    void testSelfReferencingClean() {
        final NestedSelfReferencing selfReferencing = new NestedSelfReferencing();
        ClosureCleaner.clean(selfReferencing, ExecutionConfig.ClosureCleanerLevel.RECURSIVE, true);
    }