human
Here's a good function header given the following:
I wrote the below code

    class Base:
        counter = 0
        def add(self):
            raise NotImplemented('add    not    implemented')
        def subtract(self):
            raise NotImplemented('subtract    not    implemented')
    return Base

What's a good function header?
assistant
#Here's a good function header.

@pytest.fixture()
def interface():