@classmethod
def override_accept(cls, session, languages, response=None):
    """
        Set the language preferences for the given session, thus overriding
        the preferences given in the HTTP header.
        
        :param session: the session. 
        :param languages: a list of language identifiers.
        :param response: if not None, the preference will also be
                saved as a cookie.
        """
    if not isinstance(languages, list):
        languages = [languages]
    session[cls._SESSION_KEY + '.overridden'] = languages
    if not response is None:
        pass
