from typing import Any, Generic, Optional, TypeVar from typing_extensions import assert_type from pydantic import BaseModel Tbody = TypeVar('Tbody') class Response(BaseModel, Generic[Tbody]): url: str body: Tbody class JsonBody(BaseModel): raw: str data: dict[str, Any] class HtmlBody(BaseModel): raw: str doctype: str class JsonResponse(Response[JsonBody]): pass class HtmlResponse(Response[HtmlBody]): def custom_method(self) -> None: doctype = self.body.doctype print(f'self: {doctype}') example = {'url': 'foo.com', 'body': {'raw': '....', 'doctype': 'html'}} resp = HtmlResponse.model_validate(example) resp.custom_method() assert_type(resp.body, HtmlBody) T = TypeVar('T', int, str) class HistoryField(BaseModel, Generic[T]): value: Optional[T] class DomainType(HistoryField[int]): pass thing = DomainType(value=None) assert_type(thing.value, Optional[int])