pycharm中在子类中添加一个父类没有的属性

class Car():
    """一次模拟汽车的简单尝试"""
    def __init__(self, make, model, year):
        """初始化描述汽车的属性"""
        self.make = make
        self.model = model
        self.year = year
        self.odometer_reading = 0

    def get_description_name(self):
        """返回整洁的描述性信息"""
        long_name = str(self.year) + ' ' + self.make + ' ' + self.model
        return long_name.title()

    def read_odometer(self):
        """打印一条指出汽车里程的消息"""
        print("This car has " + str(self.odometer_reading) + " miles on it.")

    def update_odometer(self, mileage):
        """
        将里程读数设置为指定的值
        禁止将里程表读数往回调
        """
        if mileage >= self.odometer_reading:
            self.odometer_reading = mileage
        else:
            print("You can't roll back an odometer!")

    def increment_odometer(self, miles):
        """将里程表读数增加指定的量"""
        self.odometer_reading += miles


class ElectricCar(Car):
    """电动汽车的独特之处"""
    def _init_(self, make, model, year):
        """
        电动汽车的独特之处
        初始化父类的属性，再初始化电动汽车特有的属性
        """
        super().__init__(make, model, year)
        self.battery_size = 70

    def describe_battery(self):
        """打印一条描述电瓶容量的消息"""
        print("This car has a " + str(self.battery_size) + "-kwh battery.")

my_tesla = ElectricCar('tesla', 'model s', 2016)
print(my_tesla.get_description_name())
my_tesla.describe_battery()
运行结果：

Traceback (most recent call last):
  File "E:/Python编程从入门到精通配套资料/Self-taught Python/electric_car.py", line 50, in 
    my_tesla.describe_battery()
  File "E:/Python编程从入门到精通配套资料/Self-taught Python/electric_car.py", line 46, in describe_battery
    print("This car has a " + str(self.battery_size) + "-kwh battery.")
AttributeError: 'ElectricCar' object has no attribute 'battery_size'