anchor.diff:  %%--------------------------------------------------------------------
   %% @private
   %% @doc
  -%% Removes link to transfer.
  +%% Removes link/links to transfer/transfers
  +%% Real link source_id will be obtained from link_root/2 function.
   %% @end
   %%--------------------------------------------------------------------
   -spec remove_links(SourceId :: virtual_list_id(), TransferId :: id() | [id()],
  
positive.code: %%--------------------------------------------------------------------
  %% @private
  %% @doc
  %% Adds link to transfer.
  %% @end
  %%--------------------------------------------------------------------
  -spec add_link(SourceId :: virtual_list_id(), TransferId :: id(),
  
negative.code:             invalidation_controller:on_new_transfer_doc(TransferDoc),
              {ok, TransferId};
          Error ->
              ?error_stacktrace("Restarting transfer ~p failed due to ~p", [TransferId, Error]),
              Error
      end.
  
  