code: public static <MK, K, V> AtomicMap<K, V> getAtomicMap(Cache<MK, ?> cache, MK key) {
        return getAtomicMap(cache, key, true);
     }
docs: Retrieves an atomic map from a given cache, stored under a given key.  If an atomic map did not exist, one is
  created and registered in an atomic fashion.
  
  @param cache underlying cache
  @param key   key under which the atomic map exists
  @param <MK>  key param of the cache
  @param <K>   key param of the AtomicMap
  @param <V>   value param of the AtomicMap
  @return an AtomicMap