docs: public static Accumulator getAccumulatorOrNull(QueryCacheContext context,
                                                     String mapName, String cacheId, int partitionId) {
          PartitionAccumulatorRegistry accumulatorRegistry = getAccumulatorRegistryOrNull(context, mapName, cacheId);
          if (accumulatorRegistry == null) {
              return null;
          }
          return accumulatorRegistry.getOrNull(partitionId);
      }