@NotNull
    private BooleanGetter getHighlighterCondition(@NotNull FoldedGroup group, final int index) {
      return () -> {
        if (!myEditors[index].getFoldingModel().isFoldingEnabled()) return false;

        for (FoldedBlock folding : group.blocks) {
          FoldRegion region = folding.getRegion(index);
          boolean visible = region != null && region.isValid() && !region.isExpanded();
          if (folding == this) return visible;
          if (visible) return false; // do not paint separator, if 'parent' folding is collapsed
        }
        return false;
      };
    }
@NotNull
    private BooleanGetter getHighlighterCondition(@NotNull FoldedGroup group, final int index)