update pypdfium2 dep and improve code quality

[felixdittrich92]

This PR:

• update pypdfium to 2.1.0 (to use with statement) and set fix to <3.0.0 to avoid [bug] doctr 0.5.1 | pypdfium2 --> AttributeError: module 'pypdfium2' has no attribute 'render_pdf_topil' #947 in upcoming releases
• improve code quality

Any feedback is welcome 🤗

[codecov]

Codecov Report

Merging #953 (d0efc48) into main (210ecc4) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #953      +/-   ##
==========================================
- Coverage   94.83%   94.81%   -0.02%     
==========================================
  Files         134      134              
  Lines        5539     5537       -2     
==========================================
- Hits         5253     5250       -3     
- Misses        286      287       +1     

Flag	Coverage Δ
unittests	94.81% <100.00%> (-0.02%)	⬇️

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Impacted Files	Coverage Δ
doctr/io/pdf.py	92.30% <100.00%> (-1.03%)	⬇️
doctr/transforms/functional/base.py	95.65% <0.00%> (-1.45%)	⬇️

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[mara004]

Looks good, then!

[frgfm]

Thanks Felix, I was about to open a PR for this specifically :)
We should update the version specifiers of other dependencies accordingly I think

[felixdittrich92]

Thanks Felix, I was about to open a PR for this specifically :)
We should update the version specifiers of other dependencies accordingly I think

😅

About the deps part let us check if we can handle this with depend-a-bot this would make it much easier (really) ^^

[frgfm]

That is a different problem though: dependabot is (to the best of my knowledge) reporting version specifier updates for security reasons

Here we need to reassess the upper and lower bound of each dep: I'll take care of it, and then set the dependabot 👍