#session_factory.py
class SessionFactory:
    def __init__(self, postgres_url: str):
        self.engine: AsyncEngine = create_async_engine(postgres_url, echo=False)
        self.async_session_maker: async_sessionmaker[AsyncSession] = async_sessionmaker(
            self.engine,
            class_=AsyncSession,
            expire_on_commit=False,
        )

    async def dispose(self) -> None:
        await self.engine.dispose()

    async def __call__(self) -> AsyncGenerator[AsyncSession, None]:
        async with self.async_session_maker() as session:
            yield session


#database.py

session_factory: SessionFactory | None = None

async def get_async_session() -> AsyncGenerator[AsyncSession, None]:
    if session_factory is None:
        raise RuntimeError("SessionFactory is not initialized")
    async for session in session_factory():
        yield session

async def get_db_stub():
    raise NotImplementedError

get_async_session_context = contextlib.asynccontextmanager(get_async_session)


#routers.py
@router.post(
    "/", response_model=ReleaseCreateResponse, status_code=status.HTTP_201_CREATED
)
async def create_release(
    user: Annotated[User, Depends(current_active_user)],
    session: Annotated[AsyncSession, Depends(get_db_stub)],
):
 ...

#main.py
@asynccontextmanager
async def lifespan(app: FastAPI):
    db.session_factory = SessionFactory(settings.db.url_postgres)

app.dependency_overrides[AsyncSession] = db.get_async_session
print(app.dependency_overrides[AsyncSession])
>> function get_async_session at 0x7fd44df4e2a0