public function getPostInstructions($format = 'plain')
    {
        $content = [];

        if (\count($this->postInstructions) == 0) {
            return null;
        }

        ksort($this->postInstructions);

        foreach ($this->postInstructions as $version => $instructions) {
            $content[] = sprintf("## %s", $version);
            foreach ($instructions as $instruction) {
                $content[] = sprintf("%s", $instruction);
            }
        }

        $content = implode("\n\n", $content);

        if ($format === 'html') {
            $content = Markdown::defaultTransform($content);
        }

        return $content;
    }