@Override
  public KnownVersion[] getSerializationVersions() {
    // TODO Auto-generated method stub
    return null;
  }
Compares scores of two entries using natural ordering. I.e. it returns -1 if the first entry's
score is less than the second one.
geode-lucene/src/main/java/org/apache/geode/cache/lucene/internal/distributed/TopEntries.java