protected function normalizeLevel($level)
    {
        if (is_int($level) && array_search($level, self::$levels) !== false) {
            return $level;
        }

        if (is_string($level) && isset(self::$levels[$level])) {
            return self::$levels[$level];
        }

        throw new Exception(
            sprintf("Unknown LogLevel: '%s'", $level)
        );
    }