anchor.diff:    A = gen_id(),
     B = gen_id(),
     C = A+B,
  -  ok = erwa_dealer:call(<<"proc.sum">>, RequestId, [], [A,B], undefined,Data),
  +  {ok,_} = erwa_dealer:call(<<"proc.sum">>, RequestId, [], [A,B], undefined,Data),
     ok = receive
            {erwa,{result, RequestId, [], [C], undefined}} -> ok
          end,
  
positive.code: 
  -spec call(Uri :: binary(), RequestId :: non_neg_integer(), Options :: list(),
             Arguments :: list(), ArgumentsKw :: list(), Data :: #data{}) ->
    ok | {error,invocation_failed} | {error, procedure_not_found}.
  call(Uri, RequestId, Options, Arguments, ArgumentsKw, #data{ets=Ets}) ->
    case ets:lookup(Ets,Uri) of
      [#procedure{uri=Uri,pids=Pids,id=ID}] ->
  
negative.code:                    callee_pids => Pids
                     },
        case erwa_invocation_sup:start_invocation(CallInfo) of
          {ok,Pid} ->
            {ok,Pid};
          _ -> {error,invocation_failed}
        end;
      [] ->
  