Replace sys.gettrace() with threading.gettrace()

[TaiSakuma]

• This PR makes the coverage more accurate.
• threading.gettrace() is new in Python 3.10

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.48%. Comparing base (5ba10e2) to head (13b872b).
Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #97      +/-   ##
==========================================
+ Coverage   85.96%   89.48%   +3.51%     
==========================================
  Files         114      114              
  Lines        4454     4411      -43     
  Branches      674      665       -9     
==========================================
+ Hits         3829     3947     +118     
+ Misses        569      421     -148     
+ Partials       56       43      -13     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.