Show Thumbs in Admin Column

Hello,
I am very new to Meta Box. I am tying to show the featured images in my admin column. The post-type is called team-member and each post has an image. I am using the following snippet in the wp plugin snippets, but as soon as I save and activate it, the site breaks it & tells me -> MB_Admin_Columns_Post is unknown ...

add_action( 'admin_init', function() {
    class My_Featured_Image_Columns extends MB_Admin_Columns_Post {
        public function columns( $columns ) {
            $columns  = parent::columns( $columns );
            $position = 'before';
            $target   = 'title';
            $this->add( $columns, 'featured_image', 'Featured Image', $position, $target );
            // Add more if you want
            return $columns;
        }
        public function show( $column, $post_id ) {
            switch ( $column ) {
                case 'featured_image':
                    the_post_thumbnail( [40, 40] );
                    break;
                // More columns
            }
        }
    }

    new My_Featured_Image_Columns( 'team-member', array() );
} );