@Override
    public boolean canMergeWith(@NotNull MergeableLineMarkerInfo<?> info) {
      if (!(info instanceof ArrowUpLineMarkerInfo)) return false;
      PsiElement otherElement = info.getElement();
      PsiElement myElement = getElement();
      return otherElement != null && myElement != null;
    }
@Override
    public boolean canMergeWith(@NotNull MergeableLineMarkerInfo<?> info)