protected function _attainClient($clientName)
    {
        if (! isset($this->lazyClientOptions[$clientName]) )
            throw new \Exception(sprintf('MongoDB Client (%s) not Registered.', $clientName));


        $conf = $this->lazyClientOptions[$clientName];
        if (! isset($conf['host']) )
            throw new \Exception(sprintf(
                '"host" Option for Client (%s) not given.'
                , $clientName
                , \Poirot\Std\flatten($conf)
            ));

        $uri        = $conf['host'];
        $uriOptions = (isset($conf['options_uri']))    ? $conf['options_uri']    : array();
        $options    = (isset($conf['options_driver'])) ? $conf['options_driver'] : array();

        $client = new MongoDB\Client($uri, $uriOptions, $options);
        return $client;
    }