public Optional<StoredImage> tryLoadImage(ImageRef ref) {
    Optional<StoredReport> report = reportStore.tryLoadReport(ref.getOwnerId(), ref.getReportId());
    Preconditions.checkArgument(report.isPresent(), "Report not found: " + ref.toString());

    return Optional.fromNullable(
        backend()
            .load()
            .type(StoredImage.class)
            .parent(report.get())
            .id(StoredImage.toKey(ref))
            .now());
  }
  private void addImage(ImageRef ref, String imageCsObjectName, BlobKey blobKey) {
    Optional<StoredReport> report = reportStore.tryLoadReport(ref.getOwnerId(), ref.getReportId());
    Preconditions.checkArgument(report.isPresent(), "Report not found: " + ref.toString());

    StoredImage image =
        StoredImage.builder()
            .setKey(StoredImage.toKey(ref))
            .setReport(Ref.create(report.get()))
            .setImageFileName(ref.getImageName())
            .setCloudStorageObjectName(imageCsObjectName)
            .setBlobKey(blobKey.getKeyString())
            .build();
    backend().save().entity(image).now();
  }