Usage of `self=None` in class Carousel triggers type checkers

[marshmallowsunshinekitten1234]

Describe the bug

class Carousel in pywa/types/templates.py, defines params in a way, that is not acceptable for type checkers. The usage of self=None to check whether or not the function is called as a class function or an instance function (same as other template components like BodyText.params(), HeaderText.params(), etc.) works at runtime, but type checkers report that None is invalid in place of self.

Faulty source code:

def params(self=None, *, cards: list[CarouselCard._Params]) -> Carousel._Params:
        """
        Fill the parameters for the carousel component.

        Args:
            [...]
        """
        [...]

All other template components work with class-level calls without type errors:

BodyText.params("hello")        # Works - no type error
HeaderImage.params(image="url") # Works - no type error  
Carousel.params(cards=[...])    # Type error: "None" not assignable to "self"

The difference is that Carousel uses explicit self=None parameter while others use the *positionals pattern in a private _params helper.

To Reproduce

import pywa.types.templates as pywa_template
# Class-level call - this triggers type error
carousel_params = pywa_template.Carousel.params(cards=[])

Actual Result (type checker):
Argument of type "None" cannot be assigned to parameter "self" of type "Carousel" in function "params"

Expected behavior

No type error; should work like other template components.

pywa version

3.9.0

python version

3.13.13

os

Debian GNU/Linux 13 (image -> python:3.13-slim)

Additional context

Suggested Fix: Change implementation to use *args-style pattern like other components.

[SirKaiMartin]

        if self is None:
            return Carousel._Params(cards=cards)
        cards_len, params_len = len(self.cards), len(cards)
        if cards_len != params_len:
            raise ValueError(
                f"Expected {cards_len} card parameters, but got {params_len}."
            )

Initialization with empty cards would cause a ValueError in params call due to len(self.cards) != len(cards).
That being said - there is no "gracefull" way of creating carousel params.

[david-lev]

Hi Kai, Could you check if inheriting from Carousel and overriding the `params()` signature with a type hint for self resolves the issue? Please try the following implementation to see if it satisfies the type checker: ```py class MyCarousel(Carousel): def params(self: "Carousel" | None = None, *, cards: list[CarouselCard._Params]) -> Carousel._Params: # call super ``` Let me know if this helps.

[marshmallowsunshinekitten1234]

Hi Kai,

Could you check if inheriting from Carousel and overriding the params()
signature with a type hint for self resolves the issue?

Please try the following implementation to see if it satisfies the type
checker:

class MyCarousel(Carousel):
	def params(self: "Carousel" | None = None, *, cards: list[CarouselCard._Params]) -> Carousel._Params:
        # call super

Let me know if this helps.

I can confirm that the type hint does make it work:

[david-lev]

Thank you for confirming the fix. Would you like to open a PR with this change into the dev branch? Otherwise, feel free to wait and we will implement the fix ourselves.