code: def register_account(self, account, portfolio_cookie=None):
          '''
          注册一个account到portfolio组合中
          account 也可以是一个策略类，实现其 on_bar 方法
          :param account: 被注册的account
          :return:
          '''
          # 查找 portfolio
          if len(self.portfolio_list.keys()) < 1:
              po = self.new_portfolio()
          elif portfolio_cookie is not None:
              po = self.portfolio_list[portfolio_cookie]
          else:
              po = list(self.portfolio_list.values())[0]
          # 把account 添加到 portfolio中去
          po.add_account(account)
          return (po, accountf register_account(self, account, portfolio_cookie=None):
          '''
          注册一个account到portfolio组合中
          account 也可以是一个策略类，实现其 on_bar 方法
          :param account: 被注册的account
          :return:
          '''
          # 查找 portfolio
          if len(self.portfolio_list.keys()) < 1:
              po = self.new_portfolio()
          elif portfolio_cookie is not None:
              po = self.portfolio_list[portfolio_cookie]
          else:
              po = list(self.portfolio_list.values())[0]
          # 把account 添加到 portfolio中去
          po.add_account(account)
          return (po, account)
docs: 注册一个account到portfolio组合中
          account 也可以是一个策略类，实现其 on_bar 方法
          :param account: 被注册的account
          :return: