bbPress.org

Hello
I am seeking help with the correct conditionals to show a custom view.
I am using
WP Version 4.8.2
bbPress Version 2.5.14
Ithemes Air Theme

I have been given the following code to insert into the functions.php file in my child theme but I am missing something here?

function custom_filter_category_layouts( $layout_id ) {
    if ( is_single() && in_category( 'news' ) )
            return 'INSERT LAYOUT NUMBER';
    
    return $layout_id;
}
add_filter( 'builder_filter_current_layout', 'custom_filter_category_layouts' );

I have tried most of what look to be the relevant conditionals at https://codex.bbpress.org/bbpress-conditional-tags/

I can get most forum views to use a theme layout I have created in Air Theme apart from the forum index page and the CHILD FORUMS (forums created with a parent)

I spoke with iThemes support and they told me it was best to ask here. If someone could help me out here it would be appreciated.

Best Regards
Mike