def req_withdraw(self, address, amount, currency, fee=0, addr_tag="", _async=False):
        """
        申请提现虚拟币
        :param address:
        :param amount:
        :param currency:btc, ltc, bcc, eth, etc ...(火币Pro支持的币种)
        :param fee:
        :param addr_tag:
        :return: {
                  "status": "ok",
                  "data": 700
                }
        """
        params = {
            'address': address,
            'amount': amount,
            'currency': currency,
            'fee': fee,
            'addr-tag': addr_tag
        }
        path = '/v1/dw/withdraw/api/create'

        return api_key_post(params, path, _async=_async)