/**
  * deactivate()
  *
  * @return void
  **/
 function deactivate()
 {
     # clean up
     xml_sitemaps::rm(WP_CONTENT_DIR . '/sitemaps');
     # drop rewrite rules
     remove_filter('mod_rewrite_rules', array($this, 'rewrite_rules'));
     xml_sitemaps::save_rewrite_rules();
     # reset status
     update_option('xml_sitemaps', 0);
 }