private function getConfigDB(ConfigInterface $config): ConfigInterface
    {
        // get current connection
        $connection = $this->getConnection();
        // Get config of required connection
        $config_db = $config->get($connection);
        try {
            if (null === $config_db) {
                throw new Exception("Connection \"$connection\" is not found in database config");
            }
        } catch (Exception $e) {
            // __constructor
        }
        return $config_db;
    }