code: protected final Map<K, V> copyMap(Map<K, Expirable<V>> map) {
      ClassLoader classLoader = cacheManager.getClassLoader();
      return map.entrySet().stream().collect(toMap(
          entry -> copier.copy(entry.getKey(), classLoader),
          entry -> copier.copy(entry.getValue().get(), classLoader)));
    }
docs: Returns a deep copy of the map if value-based caching is enabled.
  
  @param map the mapping of keys to expirable values
  @return a deep or shallow copy of the mappings depending on the store by value setting