Return all the translator users indexed by lang
        :return:

def get_users_indexed_by_lang():
        """
        Return all the translator users indexed by lang
        :return:
        """
        result = {}
        users = TransUser.objects.filter(active=True).select_related('user')
        for user in users:
            for lang in user.languages.all():
                if lang.code not in result:
                    result[lang.code] = set()
                result[lang.code].add(user)
        return result