code: def login(self, broker_name, account_cookie, account=None):
          
          res = False
          if account is None:
              if account_cookie not in self.session.keys():
                  self.session[account_cookie] = QA_Account(
                      account_cookie=account_cookie,
                      broker=broker_name
                  )
                  if self.sync_account(broker_name, account_cookie):
                      res = True
  
                  if self.if_start_orderthreading and res:
                      #
                      self.order_handler.subscribe(
                          self.session[account_cookie],
                          self.broker[broker_name]
                      )
  
          else:
              if account_cookie not in self.session.keys():
                  account.broker = broker_name
                  self.session[account_cookie] = account
                  if self.sync_account(broker_name, account_cookie):
                      res = True
                  if self.if_start_orderthreading and res:
                      #
                      self.order_handler.subscribe(
                          account,
                          self.broker[broker_name]
                      )
  
          if res:
              return res
          else:
              try:
                  self.session.pop(account_cookie)
              except:
                  pass
              return False
docs: login 登录到交易前置
  
          2018-07-02 在实盘中,登录到交易前置后,需要同步资产状态
  
          Arguments:
              broker_name {[type]} -- [description]
              account_cookie {[type]} -- [description]
  
          Keyword Arguments:
              account {[type]} -- [description] (default: {None})
  
          Returns:
              [type] -- [description]