code: function(evt) {
          var target = evt.target;
          var useElement = target && target.correspondingUseElement;
          var node = useElement ? useElement : (target || evt.srcElement);
          return node._featureId;
      }
docs: Method: getFeatureIdFromEvent
  
  Parameters:
  evt - {Object} An <OpenLayers.Event> object
  
  Returns:
  {String} A feature id or undefined.