anchor.diff:  %% @doc Remove request information, if final response is received
   %% @end
   handle_final_response(ReqInfo, #sip_response{status = Status}) when Status >= 200 ->
  +    ok = tx_demonitor(ReqInfo),
       ok = delete(ReqInfo#request_info.id),
       error_m:return(ok);
   
  
positive.code: 
  lookup_by_tx(TxPid) ->
      Requests = erlang:get(?REQUESTS),
      lists:keyfind(TxPid, #request_info.current_tx, Requests).
  
  
  store(ReqInfo) ->
  
negative.code: %% end
  do_cancel(false) ->
      {error, no_request};
  do_cancel(#request_info{cancelled = false, provisional = true} = ReqInfo) ->
      % start `CANCEL' transaction
      send_cancel(ReqInfo);
  do_cancel(ReqInfo) ->
  