public function __construct($modelType)
 {
     parent::__construct($modelType::$entityType, $modelType::$bundle);
     $this->modelType = $modelType;
 }
 private static function fetchEntities($modelType, $ids)
 {
     $query = new SpectrumQuery($modelType::$entityType, $modelType::$bundle);
     $entityInfo = entity_get_info($modelType::$entityType);
     $query->addCondition(new SpectrumPropertyCondition($modelType::$idField, 'IN', $ids));
     return $query->fetch();
 }