@Override
  public String toString() {
    return "FileIndex{" +
        "fileName='" + fileName + '\'' +
        ", fileBlobs=" + fileBlobs +
        ", fileMetadata=" + fileMetadata +
        ", checksum='" + checksum + '\'' +
        '}';
  }
Checksum of the file for verifying integrity.
samza-core/src/main/java/org/apache/samza/storage/blobstore/index/FileIndex.java