docs: public MultiMapValue merge(MultiMapMergeContainer mergeContainer,
                                 SplitBrainMergePolicy<Collection<Object>, MultiMapMergeTypes> mergePolicy) {
          SerializationService serializationService = nodeEngine.getSerializationService();
          serializationService.getManagedContext().initialize(mergePolicy);
  
          MultiMapMergeTypes mergingEntry = createMergingEntry(serializationService, mergeContainer);
          MultiMapValue existingValue = getMultiMapValueOrNull(mergeContainer.getKey());
          if (existingValue == null) {
              return mergeNewValue(mergePolicy, mergingEntry);
          }
          return mergeExistingValue(mergePolicy, mergingEntry, existingValue, serializationService);
      }