public function getAdditionalHeaders(): array
    {
        $headers = [];
        $tsfe = $this->getTsfe();
        if (!($tsfe instanceof TypoScriptFrontendController)) {
            return $headers;
        }
        // Set headers, if any
        if (\is_array($tsfe->config['config']['additionalHeaders.'])) {
            \ksort($tsfe->config['config']['additionalHeaders.']);
            foreach ($tsfe->config['config']['additionalHeaders.'] as $options) {
                $complete = \trim($options['header']);
                $parts = \explode(':', $complete, 2);
                $headers[\trim($parts[0])] = \trim($parts[1]);
            }
        }

        return $headers;
    }