Allow loading of user-trained ultralytics models

[dkloving]

Allows the user to specify a file to use when loading an ultralytics model for conversion. This is valuable for users who have already trained their models using ultralytics and don't wish to re-train.

Optional disabling of fp16 conversion is provided to users because some custom ultralytics models have been observed to not convert entirely to fp16 upon export to onnx, creating invalid onnx model files. Ideally this can be fixed to reliably convert all ultralytics models to fp16.

[codecov]

Codecov Report

Merging #79 (d3b486a) into master (2332a2c) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master      #79   +/-   ##
=======================================
  Coverage   81.79%   81.79%           
=======================================
  Files           8        8           
  Lines         736      736           
=======================================
  Hits          602      602           
  Misses        134      134           

Flag	Coverage Δ
unittests	81.79% <100.00%> (ø)

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Impacted Files	Coverage Δ
test/test_utils.py	100.00% <100.00%> (ø)

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[zhiqwang]

Hi @dkloving , Thank you for your pull request and welcome to our community.

I have a comment about the parameter naming rule, which could be more user-friendly, let me know your thoughts?

[zhiqwang]

Because of some limitations in my design here, the current parameter configuration is still a bit complicated. For example, when users train their tasks, the num_classes is not 80 in most cases, and this may cause problems. We could add a detailed usage instruction in a follow-up PR or improve this in this PR. And let me know if you prefer to improve this in this PR.

[zhiqwang]

Hi @dkloving ,

I've added some commits directly on your branch. It would be better if we could add a unit-test for updating custom model checkpoint trained from ultralytics, but let's merge this PR first for more feedbacks in the future!

If you have more questions, fell free to open a new issue or submit a PR about it. And thanks for your contribution here!