Explicitly specify arguments for to_dict and to_json methods for top-level chart objects

[binste]

This PR explicitly specifies and documents the accepted arguments for to_dict and to_json on top-level chart objects (e.g. Chart, LayerChart, ...). Previously, these methods used args and kwargs. This improves the documentation for users, allows us to type hint the arguments, and it unblocks #3071 (comment) where it is currently unclear how to best add an additional documented keyword argument format.

This might break existing code in case a user passes an unused argument, e.g. to_dict(this_argument_is_not_used=1). However, that seems acceptable to me as I don't think it was the intended behavior to allow for arbitrary arguments.

cc @jonmmease.
Maybe someone else could review it as well. Just in case I'm missing an actual use case for the args/kwargs notation

[jonmmease]

Thanks for doing this! One suggestion inline for the argument order of to_json.

[jonmmease]

While we're changing signatures, how would you feel about moving indent and sort_keys above ignore and context. Like this:

    def to_json(
        validate: bool = True,
        indent: int = 2,
        sort_keys: bool = True,
        ignore: Optional[List[str]] = None,
        context: Optional[Dict[str, Any]] = None,

I doubt this would be breaking in practice as ignore and context aren't intended for use by end users, and even if they are being used it would be even more unusual to specify validate ignore and context as positional args.

This is top of mind because I'd rather add the format argument in #3071 before ignore and context.

[binste]

Sounds good! Changed in the latest commit.

[binste]

@mattijn @joelostblom Could someone of you review this PR as well just to be sure not to break anything? No pressure at all, just a gentle ping to make sure you see this PR :)

[mattijn]

Thanks for the reminder, end of week or early next week I've time.

[mattijn]

Thanks @binste! Looks good to me too.