Support Python 3.9

[TaiSakuma]

No description provided.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 79.13043% with 24 lines in your changes missing coverage. Please review.

Project coverage is 81.94%. Comparing base (69d8fcd) to head (a7bdb24).
Report is 8 commits behind head on main.

Files with missing lines	Patch %	Lines
tests/stack/async/refs/dunder.py	0.00%	9 Missing ⚠️
tests/stack/async/refs/nested.py	0.00%	9 Missing ⚠️
tests/stack/sync/refs/dunder.py	81.81%	1 Missing and 1 partial ⚠️
tests/stack/sync/refs/nested.py	81.81%	1 Missing and 1 partial ⚠️
tests/stack/async/runner.py	91.66%	0 Missing and 1 partial ⚠️
tests/stack/sync/runner.py	91.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #57      +/-   ##
==========================================
+ Coverage   81.33%   81.94%   +0.60%     
==========================================
  Files          39       39              
  Lines        1404     1407       +3     
  Branches      264      268       +4     
==========================================
+ Hits         1142     1153      +11     
+ Misses        234      221      -13     
- Partials       28       33       +5     

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[glensc]

alright, something this I was just recently asked via issue:

• Support all supported Python versions #56

[glensc]

Imho not nice to commit dead code (commented out code) to project.

What I would do myself, is create immediately pr that drops 3.9 support and let it be in Draft state until the time comes.