code: public OkCoinFutureHoldAmount[] getFutureHoldAmount(
        CurrencyPair currencyPair, FuturesContract contractType) throws IOException {
      return okCoin.getFutureHoldAmount(
          "1", OkCoinAdapters.adaptSymbol(currencyPair), contractType.getName());
    }
docs: 获取当前可用合约总持仓量
  
  @param currencyPair
  @param contractType
  @return
  @throws IOException