docs: public static <MK, K, V> Map<K, V> getReadOnlyAtomicMap(Cache<MK, ?> cache, MK key) {
        AtomicMap<K, V> am = getAtomicMap(cache, key, false);
        if (am == null)
           return Collections.emptyMap();
        else
           return immutableMapWrap(am);
     }