ABC - must implement methods

---

examples/oop/abc/with_abc3_fake.py

from with_abc3 import Base

class Fake(Base):
    def foo(self):
        print('foo in Fake')

f = Fake('Joe')

Traceback (most recent call last):
  File "with_abc3_fake.py", line 7, in <module>
    f = Fake('Joe')
TypeError: Can't instantiate abstract class Fake with abstract methods bar