docs: function (handle) {
          if (handle) {
              var topic = handle.topic, list = listeners[topic];
              if (list) {
                  for (var i = list.length - 1; i >= 0; i--) {
                      if (list[i] === handle) {
                          list.splice(i, 1);
                      }
                  }
                  if (!list.length) {
                      delete listeners[topic];
                  }
              }
          }
      }