flake8-6.1.0 adds E721 check

[ksaur]

From Friday runner, there is another flake8 to check for related to isinstance

[codecov-commenter]

Codecov Report

Merging #730 (46917eb) into main (48472f4) will not change coverage. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #730   +/-   ##
=======================================
  Coverage   90.20%   90.20%           
=======================================
  Files          80       80           
  Lines        4676     4676           
  Branches      856      856           
=======================================
  Hits         4218     4218           
  Misses        260      260           
  Partials      198      198           

Flag	Coverage Δ
unittests	90.20% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
hummingbird/ml/convert.py	81.48% <100.00%> (ø)
...erters/_array_feature_extractor_implementations.py	100.00% <100.00%> (ø)
...bird/ml/operator_converters/_sv_implementations.py	100.00% <100.00%> (ø)
...mmingbird/ml/operator_converters/sklearn/linear.py	100.00% <100.00%> (ø)

... and 1 file with indirect coverage changes