code: def subscribe_strategy(
              self,
              strategy_id: str,
              last: int,
              today=datetime.date.today(),
              cost_coins=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'
docs: 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})