symfony_mediatheque/src/DocumentBundle/Resources/config/services.yml

services:
#    document.example:
#        class: DocumentBundle\Example
#        arguments: ["@service_id", "plain_value", "%parameter%"]

  mediatheque.twig.notice_extension:
    class: DocumentBundle\Twig\MonTwigExtension
    public: false
    tags:
      - { name: twig.extension }