abstract class in abstract class

abst.py

#
#
#
from abc import ABCMeta, abstractmethod


class Meta(metaclass=ABCMeta):

    class MetaChildren(metaclass=ABCMeta):

        @abstractmethod
        def metachil(self) -> str:
            raise NotImplementedError()

    @abstractmethod
    def meta(self) -> int:
        raise NotImplementedError()

concre.py

#
#
#

from abst import Meta


class Concre(Meta):

    class ConcreChildren(Meta.MetaChildren):
        def metachil(self) -> str:
            return "metachil!"

    def meta(self) -> int:
        a = self.ConcreChildren()
        return 2