code: public OkCoinMoreTradeResult batchTrade(String symbol, String type, String ordersData)
        throws IOException {
      OkCoinMoreTradeResult tradeResult =
          okCoin.batchTrade(apikey, symbol, type, ordersData, signatureCreator());
      return returnOrThrow(tradeResult);
    }
docs: 批量下单
  
  @param symbol
  @param type 限价单(buy/sell)
  @param ordersData "[{price:3,amount:5,type:'sell'},{price:3,amount:3,type:'buy'}]"
  最终买卖类型由orders_data 中type 为准，如orders_data不设定type 则由上面type设置为准。 若，上面type没有设置，orderData
  必须设置type
  @return
  @throws IOException