Why do we need to use __str__ method?

class Car:
    def __init__(self, make, year):
        self.make=make
        self.year=year

    def __str__(self):
        return "{} {}".format(self.make, self.year)

class Dealership:
    def __init__(self):
        self.cars=[]

    def __iter__(self):
        yield from self.cars

    def add_cars (self, car):
        self.cars.append(car)

car_one=Car("Ford", 2000)
my_dealership=Dealership()
my_dealership.add_cars(car_one)
for car in my_dealership:
    print(car)

class Dealership:
    def __init__(self):
        self.cars=["Ford Fusion","Honda Civic"]

    def __iter__(self):
        yield from self.cars

my_dealership=Dealership()
for car in my_dealership:
    print(car)