code: function() {
          if (finished === true) {
              return;
          }
          finished = true;
          req.removeAllListeners();
          if (response !== null) {
              response.removeAllListeners();
          }
          callback.apply(null, arguments);
      }
docs: Cleanup all the event listeners registered on the request, and ensure that *callback* is only called one time
  
  @note passes all the arguments passed to this function to *callback*