prepareCollections example

        $path = \sprintf('theme-config/%s.json', $themeId);

        if (!$this->filesystem->fileExists($path)) {
            throw new \RuntimeException('Cannot find theme configuration. Did you run bin/console theme:dump');
        }

        $fileContent = $this->filesystem->read($path);
        \assert(\is_string($fileContent));
        $fileObject = json_decode($fileContent, true, 512, \JSON_THROW_ON_ERROR);

        $fileObject = $this->prepareCollections($fileObject);

        $config = new StorefrontPluginConfiguration('');
        $config->assign($fileObject);

        return $config;
    }

    private function prepareCollections(array $fileObject): array
    {
        $fileObject['styleFiles'] = array_map(fn (array $file) => (new File(''))->assign($file), $fileObject['styleFiles']);