Summary

For historic reasons, Scales take the axis as the first parameter. It's use is discouraged and none of our own scales actually use it at least since#12831.

To simplify our code, we should get rid of that parameter.

Proposed fix

Do we know whether

• downstream libraries add their own Scales viaregister_scale()?
• user will directly instantiate our own Scale classes?

If so we need the full deprecation machinery:

1. Makescale_factory work with scales have or have not an initialaxis parameter. Either by try-except with/without this parameter or by introspecting the signature.
2. Introspect scale classes passed toregister_scale and warn if they still have the axis argument.
3. Make all our scales work with/without theaxis parameter by adding a suitable decorator to theirinit functions.

Otherwise, we can simplify the transition.

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Edit: Both questions areyes, so we need the full deprecation mechanism.