def flag(self, key, env=None):
        """Feature flagging system
        write flags to redis
        $ dynaconf write redis -s DASHBOARD=1 -e premiumuser
        meaning: Any premium user has DASHBOARD feature enabled

        In your program do::

            # premium user has access to dashboard?
            >>> if settings.flag('dashboard', 'premiumuser'):
            ...     activate_dashboard()

        The value is ensured to be loaded fresh from redis server

        It also works with file settings but the recommended is redis
        as the data can be loaded once it is updated.

        :param key: The flag name
        :param env: The env to look for
        """
        env = env or self.ENVVAR_PREFIX_FOR_DYNACONF or "DYNACONF"
        with self.using_env(env):
            value = self.get_fresh(key)
            return value is True or value in true_values
Feature flagging system
        write flags to redis
        $ dynaconf write redis -s DASHBOARD=1 -e premiumuser
        meaning: Any premium user has DASHBOARD feature enabled

        In your program do::

            # premium user has access to dashboard?
            >>> if settings.flag('dashboard', 'premiumuser'):
            ...     activate_dashboard()

        The value is ensured to be loaded fresh from redis server

        It also works with file settings but the recommended is redis
        as the data can be loaded once it is updated.

        :param key: The flag name
        :param env: The env to look for
        
dynaconf/base.py