修改库存

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
        )