sS lcStream_prediction2(LCStreamingCompressor comp) {
  Map<Int, OptimizedMultiSet<Int>> map = lcStream_rightPartnerMap(comp);
  //printStruct(map);
  LineComp_PairIndex.Node tail = comp.chain.tail;
  if (tail == null) null;
  OptimizedMultiSet<Int> partners = map.get(tail.value);
  //print("partners of " + tail.value + ": " + partners);
  if (partners == null) null;
  ret comp.itemToString(partners.getMostPopularEntry());
}