code: def create_blueprint(register_default_routes=True):
      
      blueprint = Blueprint(
          'invenio_i18n',
          __name__,
          template_folder='templates',
          static_folder='static',
      )
  
      if register_default_routes:
          blueprint.add_url_rule('/', view_func=set_lang, methods=['POST'])
          blueprint.add_url_rule('/<lang_code>', view_func=set_lang,
                                 methods=['GET'])
  
      return blueprint
docs: Create Invenio-I18N blueprint.