Documentation fixes

[rozyczko]

This PR includes code fixes for the documentation building process and modifications to the notebooks.

[github-actions]

This pull request does not contain a valid label. Please add one of the following labels: ['chore', 'fix', 'bugfix', 'bug', 'enhancement', 'feature', 'dependencies', 'documentation']

[rozyczko]

This still needs fixes in the magnetism notebook

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.61%. Comparing base (d5ec71a) to head (20a5466).
⚠️ Report is 334 commits behind head on develop.

❗ There is a different number of reports uploaded between BASE (d5ec71a) and HEAD (20a5466). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (d5ec71a)	HEAD (20a5466)
	1	0

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #271      +/-   ##
===========================================
- Coverage    97.90%   89.61%   -8.30%     
===========================================
  Files           43       44       +1     
  Lines         3248     2349     -899     
  Branches         0      271     +271     
===========================================
- Hits          3180     2105    -1075     
- Misses          68      195     +127     
- Partials         0       49      +49     

Flag	Coverage Δ
unittests	89.61% <ø> (?)

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see 8 files with indirect coverage changes

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