LZ小白，刚开始学Python,求教一下下面的代码哪里错了，最好能告诉我原理，因为我是按书上说的编的。
class Car():
        def __init__(self,make,model,year):
                self.make = make
                self.model = model
                self.year = year
                self.odometer_reading = 233
        def get_descriptive_name(self):
                long_name = str(self.year)+" "+self.make+' '+self.model
                return long_name.title()
        def read_odometer(self):
                print("This car has "+str(self.odometer_reading)+" miles on it.")
        def update_odometer(self,mileage):
                if mileage >=self.odometer_reading:
                        self.odometer_reading = mileage
                else:
                        print("You can't roll back an odometer!")
        def increment_odometer(self,miles):
                self.odometer_reading += miles
"""
my_new_car=Car("audi","a4",2016)
print(my_new_car.get_descriptive_name())
my_new_car.update_odometer(23)
my_new_car.read_odometer()
"""
class ElectricCar(Car):
        def __int__(self,make,model,year):
                super().__int__(make,model,year)
                self.battery_size = 70
        def describe_battery(self):
                print("this car has a "+str(self.battery_size)+"-kwh battery.")

my_tesla = ElectricCar('tesla',"model 's",2016)
print(my_tesla.get_descriptive_name())
my_tesla.describe_battery()