public function getPrivateKeyByAddress($address)
    {
        $args = [
            (string)$address
        ];

        $priv_key = null;
        try {
            $priv_key = $this->rpc->query("dumpPrivKey", $args);
        } catch (Exceptions\RPCException $e) {
            if ($e->getCode() != RPCErrorCodes::WALLET_ERROR) {
                throw $e;
            }
        }

        return $priv_key;
    }