public function addLogger(\Plop\LoggerInterface $logger /*, ... */)
    {
        $loggers = func_get_args();
        foreach ($loggers as $logger) {
            if (!($logger instanceof \Plop\LoggerInterface)) {
                throw new \Plop\Exception('Not a logger');
            }
        }

        foreach ($loggers as $logger) {
            $this[] = $logger;
        }
        return $this;
    }