Make all resumes as private

Hello,

Do you have any idea how to make all resumes private? The best option would be in functions php, but for exaple this code doesn’t work:

function force_type_private($post)
  {
  if ($post['post_type'] == 'rb_resume')
  $post['post_status'] = 'private';
  return $post;
  }
add_filter('wp_insert_post_data', 'force_type_private');