How should one deal with these issues:

/home/circleci/project/lib/matplotlib/font_manager.py:docstring of matplotlib.font_manager.afmFontProperty:8: WARNING: py:obj reference target not found: AFM
/home/circleci/project/doc/api/next_api_changes/behavior/20715-JKS.rst:4: WARNING: py:obj reference target not found: type1font.Type1Font.prop
/home/circleci/project/doc/api/next_api_changes/behavior/20715-JKS.rst:4: WARNING: py:obj reference target not found: type1font.Type1Font.transform
/home/circleci/project/doc/api/prev_api_changes/api_changes_0.91.0.rst:39: WARNING: py:class reference target not found: AFM
/home/circleci/project/doc/api/prev_api_changes/api_changes_0.98.x.rst:66: WARNING: py:meth reference target not found: matplotlib.afm.AFM.get_fullname
/home/circleci/project/doc/api/prev_api_changes/api_changes_0.98.x.rst:66: WARNING: py:meth reference target not found: matplotlib.afm.AFM.get_familyname
api/prev_api_changes/api_changes_3.5.0/behaviour.rst:230: WARNING: py:obj reference target not found: type1font.Type1Font

Should one change the previous links to point to the new one? Reformat them to not be a link? Import the required classes/functions explicitly in the to-be-removed file?

Especially: there is a PR #20715 that changes the now deprecated methods/classes. Should this be dealt with in a special way? Since it is now deprecated/private.

Please change the links in API changes to code literals using fully qualified names, e.g.

`~.type1font.Type1Font`

to

``matplotlib.type1font.Type1Font``

The API changes are historic documents for that point in time and we should not change their meaning. We can't reference with links in the current docs so the best option is literals. This is also true for the unreleased next_api_changes.

Concerning the first one, change `.AFM` to plain text for now. We currently don't build the docs for the new private modules. - I still have to decide if we want that. There are pros and cons for building docs for private parts. Anyway, for now there is nothing to link to. It might well be that font_manager.afmFontProperty() will become private as well. At least, it requires AFM as input, which is now private. But I have to have a closer look at this.

It might well be that font_manager.afmFontProperty() will become private as well.

It is only used (in the matplotlib codebase) in FontManager.addfont(), so would probably make sense. Let me know and I can do it here.

For consistency, one may also consider making ttfFontProperty private. However, that is directly used in both the cairo and svg backends, so may indicate that it maybe should stay.

Imports are slightly improved here as well.