anchor.diff:  
   -export_type([key/0, args/0, state/0, server/0, request/0, response/0]).
   
  +-define(monitor_internal_calls, 1).
  +
   %%%===================================================================
   %%% API
   %%%===================================================================
  
positive.code:         {error, Reason} ->
              {error, Reason}
      end.
  
  %%--------------------------------------------------------------------
  %% @doc
  
negative.code: %%--------------------------------------------------------------------
  -spec call(module(), args(), key(), request(), timeout(), non_neg_integer()) ->
      {response(), pid()} | {error, Reason :: term()}.
  -ifdef(monitor_internal_calls).
  call(_Module, _Args, _Key, _Request, _Timeout, 0) ->
      {error, timeout};
  call(Module, Args, Key, Request, Timeout, Attempts) ->
  