Devolver el tipo de la misma clase:

from typing import Self

class Foo:
   def returns_self(self) -> Self:
      return self

Alias de tipo:

from typing import TypeAlias

Factors: TypeAlias = list[int]

Definición de un tipo (en este caso self):

from typing import TypeVar

Self = TypeVar("Self", bound="Foo")

class Foo:
   def returns_self(self: Self) -> Self:
      return self

Several types:

Union[Union[int, str], float] == Union[int, str, float]
Union[int] == int

Type or None: Optional[X] is equivalent to X | None (or Union[X, None]).

Optional[str]

Class type:

class ShopifyPostView(MethodView):
    shopify_request_schema: t.Union[
        t.Type[ShopifyPaymentsRequest],
        t.Type[ShopifyRefundsRequest],
    ] = None