Symfony 2：：我们可以在前置配置中使用条令吗。。？

我们可以在前置配置中使用原则吗

<?php
    namespace Test\FrontBundle\DependencyInjection;

    use Symfony\Component\DependencyInjection\ContainerBuilder;
    use Symfony\Component\Config\FileLocator;
    use Symfony\Component\HttpKernel\DependencyInjection\Extension;
    use Symfony\Component\DependencyInjection\Loader;
    use Symfony\Component\Yaml\Parser;
    use Lexik\Bundle\TranslationBundle\DependencyInjection\LexikTranslationExtension;
    use Symfony\Component\Config\Definition\Processor;
    use Symfony\Component\DependencyInjection\Extension\PrependExtensionInterface;
    use Symfony\Component\DependencyInjection\Loader\YamlFileLoader;
    use Doctrine\ORM\EntityManager;
    class TestFrontExtension extends Extension implements PrependExtensionInterface
    {
        /**
         * {@inheritdoc}
         */
        public function load(array $configs, ContainerBuilder $container)
        {
            $configuration = new Configuration();
            $config = $this->processConfiguration($configuration, $configs);
            $loader = new Loader\YamlFileLoader($container, new FileLocator(__DIR__.'/../Resources/config'));
            $loader->load('services.yml');
        }
        public function prepend(ContainerBuilder $container)
        {
            $processor = new Processor();
            $configuration = new Configuration();
            $extension = new LexikTranslationExtension();
            $container->registerExtension($extension);
            $container->loadFromExtension($extension->getAlias());          
            $configs = $container->getExtensionConfig($extension->getAlias());
            $em = new EntityManager();
            // $em = $container->get('doctrine.orm.default_entity_manager');
            $language_params = $em->getRepository('AdminBundle:Language')->findAll();           
            $language_data = array();
            foreach($language_params as $code)
            {
                $language_code = $code->getCode();
                if(!empty($language_code)):
                    $lcode = strtolower($language_code);
                    $language_data[] = $lcode;
                endif;
            }
            echo "<pre>";
            print_r($language_data);
            die();          
            $container->prependExtensionConfig('lexik_translation', $configss);
        }
    }
?>