public function listIndex($label, $conn = null)
    {
        $command = $this->invoke('neo.list_index_command', $conn);
        $command->setArguments($label);
        $httpResponse = $command->execute();

        $response = $this->handleHttpResponse($httpResponse);
        $propertiesIndexed = [];
        foreach ($response->getBody() as $index) {
            foreach ($index['property_keys'] as $key) {
                $propertiesIndexed[] = $key;
            }
        }
        if ($response instanceof \GraphAware\NeoClient\Formatter\Response) {
            return new \GraphAware\NeoClient\Formatter\Response(new PsrResponse(200, array(), json_encode($propertiesIndexed)));
        }
        $response->setBody($propertiesIndexed);

        return $response;
    }