Update python syntax + flake8/pylint fixes

[ewu63]

Purpose

This PR updates python syntax via pyupgrade, and I also made some pylint/flake8 fixes.

Type of change

What types of change is it?
Select the appropriate type(s) that describe this PR

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (non-backwards-compatible fix or feature)
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Documentation update
• Maintenance update
• Other (please describe)

Testing

Existing tests pass.

Checklist

Put an x in the boxes that apply.

• I have run flake8 and black to make sure the code adheres to PEP-8 and is consistently formatted
• I have run unit and regression tests which pass locally with my changes
• I have added new tests that prove my fix is effective or that my feature works
• I have added necessary documentation

[codecov]

Codecov Report

Merging #17 (bd370c4) into master (f1726c3) will increase coverage by 0.59%.
The diff coverage is 50.00%.

❗ Current head bd370c4 differs from pull request most recent head 22e224c. Consider uploading reports for the commit 22e224c to get more accurate results

@@            Coverage Diff             @@
##           master      #17      +/-   ##
==========================================
+ Coverage   72.84%   73.44%   +0.59%     
==========================================
  Files           3        3              
  Lines         372      369       -3     
==========================================
  Hits          271      271              
+ Misses        101       98       -3     

Impacted Files	Coverage Δ
multipoint/multiPointSparse.py	77.81% <45.00%> (ø)
multipoint/utils.py	45.28% <66.66%> (+2.42%)	⬆️

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