/**
  * Get a SolrService
  * 
  * @param string $core Optional core name
  * @return SolrService_Core
  */
 static function service($core = null)
 {
     $options = self::solr_options();
     if (!self::$service_singleton) {
         self::$service_singleton = Object::create($options['service'], $options['host'], $options['port'], $options['path']);
     }
     if ($core) {
         if (!isset(self::$service_core_singletons[$core])) {
             self::$service_core_singletons[$core] = self::$service_singleton->serviceForCore(singleton($core)->getIndexName());
         }
         return self::$service_core_singletons[$core];
     } else {
         return self::$service_singleton;
     }
 }