@Override
    public List<DescriptorDigest> getDiffIds() throws DigestException {
      List<DescriptorDigest> processedDiffIds = new ArrayList<>(rootFs.layers.size());
      for (String diffId : rootFs.layers) {
        processedDiffIds.add(DescriptorDigest.fromDigest(diffId.trim()));
      }
      return processedDiffIds;
    }
Return a list of diff ids of the layers in the image.

@return a list of diff ids
@throws DigestException if a digest is invalid
jib-core/src/main/java/com/google/cloud/tools/jib/docker/CliDockerClient.java