Object Oriented Programming - General Questions

What is the output of the following code?

class A: pass
class B(A): pass
print(isinstance(B(), A), issubclass(A, B))

Which module provides abstract base classes?

What is the output of the following code?

class Animal:
    def sound(self):
        return 'generic'
class Cat(Animal):
    def sound(self):
        return 'meow'
print(Cat().sound(), Animal().sound())

What is the output of the following code?

class Bag:
    def __init__(self):
        self.items = [1, 2, 3]
    def __len__(self):
        return len(self.items)
print(len(Bag()))

What is self in a method?