converting the type comments in this module to annotations with com2ann breaks the code, cf. postponed evaluation of annotations

factory.py

from typing import Optional
from typing import List

class Pizza:
    def __init__(self, ingredients=None):
        # type: (Optional[List[str]]) -> None
        if ingredients is None:
            self.ingredients = []
        else:
            self.ingredients = ingredients

    def __repr__(self):
        # type: () -> str
        return "This is a Pizza with %s on it" % " ".join(self.ingredients)

    @classmethod
    def pizza_salami(cls):
        # type: () -> Pizza
        return cls(ingredients=["Salami", "Cheese", "Onions"])