private function processOptions()
    {
        $claims = [];

        foreach ($this->options as $name => $value) {
            switch ($name) {
                case 'expires':
                    if ($value instanceof \DateTime) {
                        $claims['exp'] = $value->getTimestamp();
                    }
                    break;
                case 'notBefore':
                    if ($value instanceof \DateTime) {
                        $claims['nbf'] = $value->getTimestamp();
                    }
                    break;
                default:
                    $claims[$name] = $value;
                    break;
            }
        }

        return $claims;
    }