code: function (result, cb) {
          var self = this;
          this.swfClient.respondActivityTaskCompleted({
              result: stringify(result),
              taskToken: this.config.taskToken
          }, function (err) {
              if (self.onDone) {
                  self.onDone();
              }
              if (cb) {
                  cb(err);
              }
  
          });
  
      }
docs: Sends a "RespondActivityTaskCompleted" to AWS.
  @param {Mixed} result - Result of the activity (will get stringified in JSON if not a string)
  @param {Function} [cb] - callback