code: def contract_multiplier(self):
          
          try:
              return self.__dict__["contract_multiplier"]
          except (KeyError, ValueError):
              raise AttributeError(
                  "Instrument(order_book_id={}) has no attribute 'contract_multiplier' ".format(self.order_book_id)
              )
docs: [float] 合约乘数，例如沪深300股指期货的乘数为300.0（期货专用）