code: def value_percent(self):
          
          accounts = Environment.get_instance().portfolio.accounts
          if DEFAULT_ACCOUNT_TYPE.STOCK.name not in accounts:
              return 0
          total_value = accounts[DEFAULT_ACCOUNT_TYPE.STOCK.name].total_value
          return 0 if total_value == 0 else self.market_value / total_value
docs: [float] 获得该持仓的实时市场价值在股票投资组合价值中所占比例，取值范围[0, 1]