code: public List<DynamoDBMapper.FailedBatch> batchWrite(Iterable<T> objectsToWrite, Iterable<T> objectsToDelete) {
          return mapper.batchWrite(objectsToWrite, objectsToDelete);
      }
docs: Saves and deletes the objects given using one or more calls to the
  batchWriteItem API.
  @param objectsToWrite The objects to write.
  @param objectsToDelete The objects to delete.
  @return The list of failed batches.
  @see com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapper#batchWrite