def batchcancel_openOrders(self, acc_id, symbol=None, side=None, size=None, _async=False):
        """
        批量撤销未成交订单
        :param acc_id: 帐号ID
        :param symbol: 交易对
        :param side: 方向
        :param size:
        :param _async:
        :return:
        """

        params = {}
        path = '/v1/order/batchCancelOpenOrders'
        params['account-id'] = acc_id
        if symbol:
            params['symbol'] = symbol
        if side:
            assert side in ['buy', 'sell']
            params['side'] = side
        if size:
            params['size'] = size

        return api_key_get(params, path, _async=_async)