symfony-billing/BillingBundle/DependencyInjection/BillingExtension.php

<?php

namespace Bluesquare\BillingBundle\DependencyInjection;

use Symfony\Component\DependencyInjection\ContainerBuilder;
use Symfony\Component\DependencyInjection\Extension\Extension;
use Symfony\Component\DependencyInjection\Loader\YamlFileLoader;
use Symfony\Component\Config\FileLocator;

class BillingExtension extends Extension
{
    public function load(array $configs, ContainerBuilder $container)
    {
        $loader = new YamlFileLoader($container, new FileLocator(__DIR__.'/../Resources/config'));

        $loader->load('services.yaml');

        $configuration = new Configuration();

        $config = $this->processConfiguration($configuration, $configs);

        return $config;
    }

    public function getAlias()
    {
        return 'bluesquare.billing_bundle';
    }
}