anchor.diff:  -type fold_acc() :: datastore_links:fold_acc().
   -type fold_opts() :: datastore_links:fold_opts().
   -type state() :: #state{}.
  +-type tp_key() :: datastore:key() | non_neg_integer()
  +    | {doc | links, datastore:key()}.
   
   %%%===================================================================
   %%% API
  
positive.code: %% Multiplies requests handling error.
  %% @end
  %%--------------------------------------------------------------------
  -spec multi_call(ctx(), {doc | links, key()}, atom(), list(), non_neg_integer()) ->
      term().
  multi_call(Ctx, Key, Function, Args, Size) ->
      case call(Ctx, Key, Function, Args) of
  
negative.code: %% with a key.
  %% @end
  %%--------------------------------------------------------------------
  -spec call(ctx(), tp_key(), atom(), list()) -> term().
  call(Ctx, Key, Function, Args) ->
      case call_async(Ctx, Key, Function, Args) of
          {ok, Ref} -> wait(Ref);
  