/**
  * {@inheritdoc}
  */
 protected function build(Definition $definition, \Model $model, DefinitionMapper $mapper, Filter $filter = null, Definition $parent = null)
 {
     if (!$definition instanceof LayerGroup) {
         return;
     }
     $collection = LayerModel::findBy(array('pid=?', 'active=1'), array($model->id), array('order' => 'sorting'));
     if ($collection) {
         foreach ($collection as $layerModel) {
             $layer = $mapper->handle($layerModel);
             if ($layer instanceof Layer) {
                 $definition->addLayer($layer);
             }
         }
     }
 }