instantiate_from_csv类方法应该从名为“items.csv”的CSV文件中读取数据，为文件中的每行数据创建新的Item对象，并将对象添加到all列表中。然后遍历字典列表并创建新的Item**对象，但由于价格和数量应该是浮点数和整数，我用float（）和int（）方法转换它们，但我有一个错误
下面是错误：

price=float(item.get('price')),
          ^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: float() argument must be a string or a real number, not 'NoneType'

下面是代码：

import csv
class Item:
    pay_rate = 0.8
    all = []
    def __init__(self, name: str, price: int , quantity: int):
        #run validation to the received arguments
        assert quantity >= 0, "The {quantity} quantity should be greater or equal to zero"
        assert price >= 0, "The price should be greater or equal to zero"

        #assigned to the self object      
        self.name = name
        self.price = price
        self.quantity = quantity

        #Action to execute
        Item.all.append(self)

    def calculate_total_price(self):
       return self.price * self.quantity

    def apply_discount(self):
        self.price = self.price * self.pay_rate

    @classmethod
    def intantiate_from_csv(cls):
        with open('items.csv', 'r') as f:
            reader = csv.DictReader(f)
            items = list(reader)
            # print(items)

        for item in items:
            Item(
                name=item.get('name'),
                price=float(item.get('price')),
                quantity=int(item.get('quantity')),
            )

    def __repr__(self):
        return f"Item('{self.name}', {self.price}, {self.quantity})"

# items

Item.intantiate_from_csv()
print(Item.all)