Forcing two or more custom post type to be private

You can add multiple compared condition variable in single if condition using logical OR operator.

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function force_type_private($post)
    {
        if ($post['post_type'] == 'my_post_type1' || $post['post_type'] == 'my_post_type2') {
            $post['post_status'] = 'private';
        }
        return $post;
    }
    add_filter('wp_insert_post_data', 'force_type_private ');