Clean code, update tests

[TaiSakuma]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 95.31250% with 12 lines in your changes missing coverage. Please review.

Project coverage is 85.59%. Comparing base (3fbd0ad) to head (8307696).

Files	Patch %	Lines
nextline/main.py	14.28%	12 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #71      +/-   ##
==========================================
- Coverage   85.62%   85.59%   -0.03%     
==========================================
  Files         113      113              
  Lines        4473     4368     -105     
  Branches      702      661      -41     
==========================================
- Hits         3830     3739      -91     
+ Misses        586      572      -14     
  Partials       57       57              

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