def subscribe_strategy(
            self,
            strategy_id: str,
            last: int,
            today=datetime.date.today(),
            cost_coins=10
    ):
        """订阅一个策略

        会扣减你的积分

        Arguments:
            strategy_id {str} -- [description]
            last {int} -- [description]

        Keyword Arguments:
            today {[type]} -- [description] (default: {datetime.date.today()})
            cost_coins {int} -- [description] (default: {10})
        """

        if self.coins > cost_coins:
            order_id = str(uuid.uuid1())
            self._subscribed_strategy[strategy_id] = {
                'lasttime':
                last,
                'start':
                str(today),
                'strategy_id':
                strategy_id,
                'end':
                QA_util_get_next_day(
                    QA_util_get_real_date(str(today),
                                          towards=1),
                    last
                ),
                'status':
                'running',
                'uuid':
                order_id
            }
            self.coins -= cost_coins
            self.coins_history.append(
                [
                    cost_coins,
                    strategy_id,
                    str(today),
                    last,
                    order_id,
                    'subscribe'
                ]
            )
            return True, order_id
        else:
            # return QAERROR.
            return False, 'Not Enough Coins'