code: function() {
        inputEx.TypeField.superclass.initEvents.call(this); 
        
        // "Toggle the properties panel" button :
        Event.addListener(this.button, 'click', this.onTogglePropertiesPanel, this, true);
        
        // Prevent the button to receive a "click" event if the propertyPanel doesn't catch it
        Event.addListener(this.propertyPanel, 'click', function(e) { Event.stopPropagation(e);}, this, true);
        
        // Listen the "type" selector to update the groupOptions
        // Hack the type selector to rebuild the group option
        this.typeSelect.updatedEvt.subscribe(this.rebuildGroupOptions, this, true);
     }
docs: Adds 2 event listeners:
  - on the button to toggel the propertiesPanel