code: function(customEvent, callback, context, filter, prepend) {
              return this._addMultiSubs(false, customEvent, callback, context, filter, prepend);
          }
docs: Subscribes to a customEvent. The callback will be executed `after` the defaultFn.
  
  @static
  @method after
  @param customEvent {String|Array} the custom-event (or Array of events) to subscribe to. CustomEvents should
  have the syntax: `emitterName:eventName`. Wildcard `*` may be used for both `emitterName` as well as `eventName`.
  If `emitterName` is not defined, `UI` is assumed.
  @param callback {Function} subscriber:will be invoked when the event occurs. An `eventobject` will be passed
  as its only argument.
  @param [context] {Object} the instance that subscribes to the event.
  any object can passed through, even those are not extended with event-listener methods.
  Note: Objects who are extended with listener-methods should use instance.after() instead.
  @param [filter] {String|Function} to filter the event.
  Use a String if you want to filter DOM-events by a `selector`
  Use a function if you want to filter by any other means. If the function returns a trully value, the
  subscriber gets invoked. The function gets the `eventobject` as its only argument and the context is
  the subscriber.
  @param [prepend=false] {Boolean} whether the subscriber should be the first in the list of after-subscribers.
  @return {Object} handler with a `detach()`-method which can be used to detach the subscriber
  @since 0.0.1