public function createAddress(string $secretSpendKey = null, string $publicSpendKey = null):JsonResponse
    {
        $params = [];

        if (!is_null($secretSpendKey)) $params['secretSpendKey'] = $secretSpendKey;
        if (!is_null($publicSpendKey)) $params['publicSpendKey'] = $publicSpendKey;

        return $this->rpcPost('createAddress', $params);
    }