@Nullable
  public Int2IntMap getNewToOldLineMapping() {
    if (myNewToOldLines == null) {
      myNewToOldLines = doGetLineMapping(false);
      if (myNewToOldLines == null) return null;
    }
    return myNewToOldLines.get();
  }
@Nullable
  public Int2IntMap getNewToOldLineMapping()