Getting frontmatter data is not working as expected

[abdul-alhasany]

Hi

I added the front matter extensions to the markdown converter. As per instruction in documentation I tired:

if ($result instanceof RenderedContentWithFrontMatter) {
    $frontMatter = $result->getFrontMatter();
}

However, there is no output. When I try:

$result ->data->get('front_matter')

I get the frontmatter data. Which means the extensions is added but the above code is not working.

Is there something I have to do, or could it be a case of outdated documentation?