Fix inference inconsistency compare with ultralytics

[zhiqwang]

No description provided.

[codecov]

Codecov Report

Merging #31 (1008005) into master (0af9a2d) will increase coverage by 33.60%.
The diff coverage is 97.43%.

@@             Coverage Diff             @@
##           master      #31       +/-   ##
===========================================
+ Coverage   37.02%   70.62%   +33.60%     
===========================================
  Files          33        8       -25     
  Lines        2847      606     -2241     
===========================================
- Hits         1054      428      -626     
+ Misses       1793      178     -1615     

Flag	Coverage Δ
unittests	70.62% <97.43%> (+33.60%)	⬆️

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Impacted Files	Coverage Δ
test/test_torchscript.py	97.43% <ø> (-0.24%)	⬇️
test/test_image_utils.py	96.87% <96.87%> (ø)
test/test_engine.py	97.05% <100.00%> (+0.08%)	⬆️
test/test_models.py	92.95% <100.00%> (-0.15%)	⬇️
test/common_utils.py	52.99% <0.00%> (-0.21%)	⬇️
test/test_onnx.py	85.13% <0.00%> (-0.20%)	⬇️
test/dataset_utils.py	0.00% <0.00%> (ø)
datasets/voc_eval.py
datasets/coco.py
... and 16 more

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