[Fix] SVT dataset: clip box values and add shape and label check

[felixdittrich92]

This PR:

• clip box values and add shape and label check

Any feedback is welcome 🤗

Please merge #954 before this one :)

[codecov]

Codecov Report

Merging #955 (abac30c) into main (210ecc4) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #955   +/-   ##
=======================================
  Coverage   94.83%   94.83%           
=======================================
  Files         134      134           
  Lines        5539     5540    +1     
=======================================
+ Hits         5253     5254    +1     
  Misses        286      286           

Flag	Coverage Δ
unittests	94.83% <100.00%> (+<0.01%)	⬆️

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

Impacted Files	Coverage Δ
doctr/datasets/svt.py	97.67% <100.00%> (+0.05%)	⬆️

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[frgfm]

Looks good to me! Only one question about the target format

[charlesmindee]

Thanks! LGTM