public function getUniqueConstraints($conn = null)
    {
        $command = $this->invoke('neo.get_constraints_command', $conn);
        $httpResponse = $command->execute();

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

        $responseO->setBody($constraints);

        return $responseO;
    }