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