anchor.diff:          TreeId, Links
       ]);
   mark_links_deleted(Ctx, Key, TreeId, Link) ->
  -    hd(mark_links_deleted(Ctx, Key, TreeId, [Link])).
  +    ?MODULE:hd(mark_links_deleted(Ctx, Key, TreeId, [Link])).
   
   %%--------------------------------------------------------------------
   %% @doc
  
positive.code: get_links(Ctx, Key, TreeIds, LinkNames) when is_list(LinkNames) ->
      datastore_apply(Ctx, Key, fun datastore:get_links/4, get_links, [TreeIds, LinkNames]);
  get_links(Ctx, Key, TreeIds, LinkName) ->
      hd(get_links(Ctx, Key, TreeIds, [LinkName])).
  
  %%--------------------------------------------------------------------
  %% @doc
  
negative.code: add_links(Ctx, Key, TreeId, Links) when is_list(Links) ->
      datastore_apply(Ctx, Key, fun datastore:add_links/4, add_links, [TreeId, Links]);
  add_links(Ctx, Key, TreeId, Link) ->
      ?MODULE:hd(add_links(Ctx, Key, TreeId, [Link])).
  
  %%--------------------------------------------------------------------
  %% @doc
  