* Make support/python/mkdocstrings_handlers/cxx/__init__.py PEP compliant.
* Rollback minor change in __init__ signature.
* Rollback minor change in __init__ signature.
* Fix previous commit.
* Add 'from __future__ import annotations' to fix Python 3.8 error when using operator '|'.
* Change doxyxml2html([n]) to doxyxml2html(list(n)) as suggested by Victor.
Change convert_type return type to Optional[str].