How to pre_get_posts example in WordPress?

function wps_modify_main_query($query) {

if (!is_admin() && $query->is_main_query()) {

$query->set('post_type', 'download');
$query->set('orderby', 'ID');
$query->set('order', 'ASC');

}

}
add_action('pre_get_posts', 'wps_modify_main_query');