protected function getOperationValue($value) {
        
        if(is_a($value, '\\oat\\search\\base\\QueryBuilderInterface')) {
            $serialyser = new self();
            $serialyser->setDriverEscaper($this->getDriverEscaper())->setServiceLocator($this->getServiceLocator())->setOptions($this->getOptions());
            $value = $serialyser->setCriteriaList($value)->prefixQuery()->serialyse();
        }
        return $value;
    }