code: private Future removeExistingKeys(List<Data> keys) {
          OperationService operationService = mapServiceContext.getNodeEngine().getOperationService();
          Operation operation = new RemoveFromLoadAllOperation(name, keys);
          return operationService.invokeOnPartition(MapService.SERVICE_NAME, operation, partitionId);
      }
docs: Removes keys already present in the partition record store from
  the provided keys list.
  This is done by sending a partition operation. This operation is
  supposed to be invoked locally and the provided parameter is supposed
  to be thread-safe as it will be mutated directly from the partition
  thread.
  
  @param keys the keys to be filtered
  @return the future representing the pending completion of the key
  filtering task