docs: public OkCoinTradeResult futuresTrade(
        String symbol,
        String type,
        String price,
        String amount,
        FuturesContract contract,
        int matchPrice,
        int leverRate)
        throws IOException {
  
      OkCoinTradeResult tradeResult =
          okCoin.futuresTrade(
              apikey,
              symbol,
              contract.getName(),
              type,
              price,
              amount,
              matchPrice,
              leverRate,
              signatureCreator());
      return returnOrThrow(tradeResult);
    }