docs: def modify_stock(self, card_id, n):
          """
          修改库存
          """
          if n == 0:
              return
          card_data = {
              'card_id': card_id,
          }
          if n > 0:
              card_data['increase_stock_value'] = n
          elif n < 0:
              card_data['reduce_stock_value'] = -n
          return self._post(
              'card/modifystock',
              data=card_data
          )