docs/typehints/comments – simplify.simplify_clusters()

[jGaboardi]

This PR:

• adds docs & typehints for simplify.simplify_clusters()
• adds & updates some comments
• xref testing, refactor, & docstrings #20

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.8%. Comparing base (43e1da6) to head (c060edc).
Report is 3 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #128   +/-   ##
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  Coverage   98.8%   98.8%           
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  Files          6       6           
  Lines        962     962           
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  Hits         950     950           
  Misses        12      12           

Files with missing lines	Coverage Δ
sgeop/simplify.py	98.0% <100.0%> (ø)