fix: pyflakes style

[jorgepiloto]

This is related with #296. It enables the PyFlakes (F) rule. Most of the changes include:

• Remove unused variables
• Remove duplicated tests
• Usage of __all__ in __init__ files

[codecov]

Codecov Report

Attention: Patch coverage is 60.00000% with 6 lines in your changes missing coverage. Please review.

Project coverage is 87.35%. Comparing base (b7f89f7) to head (6f89fce).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1953      +/-   ##
==========================================
- Coverage   88.41%   87.35%   -1.07%     
==========================================
  Files          89       89              
  Lines       10258    10248      -10     
==========================================
- Hits         9070     8952     -118     
- Misses       1188     1296     +108     

[jorgepiloto]

Checking the decrease in coverage. Some tests were duplicated and exactly the same.

[jorgepiloto]

This test slightly differs from another named exactly the same within this file. To be reviewed...

[jorgepiloto]

Progress on this for the next days:

• Restore unused properties
• Verify their value in Pytest

This solves the issues for coverage and codacy.

Example:

mesh = Object.mesh
assert np.assert_allclose(mesh, mesh_expected, atol, rtol)

[moe-ad]

I do not see how we can boost coverage on the erring lines. Most are modified f-strings or exception statements. If the lines are really being covered before now, there is no reason why they shouldn't be covered after the changes, at least I can't think of any.