code: public function process(ContainerBuilder $container)
      {
          if (!$container->hasDefinition($this->validator) && !$container->hasAlias($this->validator)) {
              return;
          }
  
          $validator = $container->findDefinition($this->validator);
          foreach ($container->findTaggedServiceIds($this->tag) as $id => $tags) {
              $definition = $container->getDefinition($id);
  
              foreach ($tags as $tag) {
                  $validator->addMethodCall('register', array($definition));
              }
          }
      }
docs: {@inheritdoc}