Given this code snippet, what will be the output?

Given this code snippet, what will be the output?

class User:
    def __init__(self, name):
        self.name = name

class Group:
    def __init__(self):
        self.users = []
    def add_user(self, user):
        self.users.append(user)

group = Group()
user1 = User('Alice')
group.add_user(user1)
print(len(group.users))