In gxt 3.0.1, this code allow enter custom value in ComboBox:

Code:
flight = new ComboBox<Flight>(new ComboBoxCell<Flight>(flightStore, flightProp.flightStr()) {
      @Override
      protected Flight selectByValue(String value) {
        Flight val = super.selectByValue(value);
        if (val == null) {
          // custom logic for creating new objects goes here
          val = new Flight(value);
        }
        return val;
      }
    });
in 3.1.1 - code does not work
How to implement this functionality in the gxt 3.1.1 ?