private function _getClient(): ClientInterface
    {
        if (! $this->client instanceof ClientInterface) $this->client = new Client($this->clientConfig);
        return $this->client;
    }
private function _getClient(): ClientInterface
    {
        if (! $this->client instanceof ClientInterface) $this->client = new Client($this->clientConfig);
        return $this->client;
    }
private function _getClient ( ) : ClientInterface { if ( ! $ this -> client instanceof ClientInterface ) $ this -> client = new Client ( $ this -> clientConfig ) ; return $ this -> client ; }
get a client implements \GuzzleHttp\ClientInterface
@return ClientInterface
get a client implements \ GuzzleHttp \ ClientInterface