code: private static JsonNode getBlobSum(boolean isSchemeVersion1, JsonNode fsLayer) {
          JsonNode blobSum;
          if (isSchemeVersion1) {
              blobSum = fsLayer.get("blobSum");
          } else {
              blobSum = fsLayer.get("digest");
          }
  
          if (blobSum == null) {
              throw new IllegalStateException("Could not find 'blobSub' or 'digest' in manifest");
          }
  
          return blobSum;
      }
docs: Return blob sum depend on scheme version.
  
  @param isSchemeVersion1
  @param fsLayer
  @return