sclass ChessOCR_BoardsFound {
  sclass ByFEN {
    double bestScore;
    new Set<Pair<Rect, Double>> boardPositions;
  }
  
  Map<S, ByFEN> byFEN;
  
  void add(ChessOCR_RecognizedBoard b) {
    if (b == null || b.fen == null) ret;
    ByFEN bf = getOrCreate ByFEN(byFEN, b.fen);
    bf.bestScore = max(bf.bestScore, b.score);
    if (b.rectInOriginalImage != null)
      bf.boardPositions.add(pair(b.rectInOriginalImage, b.score));
  }
}