Code Snippet Error in KB?

I was trying to use the code snippet below which is displayed at https://docs.metabox.io/extensions/mb-relationships/

and when I wrap it to make a function

add_action( 'mb_relationships_init', function() {
MB_Relationships_API::register( array(
    'id'   => 'posts_to_pages',
    'from' => array(
        'object_type'  => 'post',
        'admin_column' => 'true',  // THIS!
    ),
    'to'   => array(
        'object_type'  => 'post',
        'post_type'    => 'page',
        'admin_column' => 'after title', // THIS!
) );
} );

there is a syntax error – I don’t know how to close the script properly. since all of the other snippets work perfectly, I thought I would bring this to your attention.