from abc import ABC, abstractmethod
from typing import *


class Model:
    pass


class Context:
    pass


T = TypeVar('T', Context)


class ContextProvider(ABC, Generic[T]):
    @abstractmethod
    def make_context(self) -> T:
        pass


class DatabaseWorker(ABC):
    @abstractmethod
    def perform_work(self,
                     prepared_data: Dict[str, Any],
                     context_provider: ContextProvider[Context]) -> Optional[List[Model]]:
        pass


class ConcreteContext(Context):
    def __init__(self):
        self.foo = 'foo'
        self.bar = 'bar'


C = TypeVar('C', ConcreteContext)


class ConcreteContextProvider(ContextProvider, Generic[C]):
    def make_context(self) -> C:
        return ConcreteContext()


class ConcreteDatabaseWorker(DatabaseWorker):
    def perform_work(self,
                     prepared_data: Dict[str, Any],
                     context_provider: ContextProvider[ConcreteContext]) -> Optional[List[Model]]:
        pass