public function deleteAQLFunctionsByNamespace($namespace)
    {
        try {
            $userFunction = new AqlUserFunction($this->_toolbox->getConnection());
            $userFunction->unregister($namespace, true);
        } catch (\Exception $e) {
            $normalised = $this->_toolbox->normaliseDriverExceptions($e);
            throw new ServerException($normalised['message'], $normalised['code']);
        }

        return true;
    }