Fix broken impl and multiple typing issues

from __future__ import annotations

from typing import Any

from collections.abc import Sequence

from typing import Any, Self

from sqlalchemy import select

from sqlalchemy.orm import DeclarativeBase, MappedColumn

from poolpay import db

        return None

    @classmethod

    def get_all(cls) -> list[Retrievable]:

    def get_all(cls) -> Sequence[Self]:

        """

        Return all instances of this type.

        """

        return db.session.execute(

            db.select(cls).order_by(cls.get_canonical_order_column())

        ).scalars()

        if not db.session:

            raise RuntimeError("db.session has not been initialized")

        return (

            db.session.execute(select(cls).order_by(cls.get_canonical_order_column()))

            .scalars()

            .all()

        )

    @classmethod

    def get_only(cls, primary_key: Any) -> Retrievable | None:

    def get_only(cls, primary_key: Any) -> Self | None:

        """

        Return the instance of this type with the given primary key or None if it doesn't exist.

        """

        if not db.session:

            raise RuntimeError("db.session has not been initialized")

        return db.session.get(cls, primary_key)

    @property