Fix bug with from_argparse and finetune

[ethanwharris]

What does this PR do?

Fixes # (issue)

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[codecov]

Codecov Report

Merging #382 (330ebe0) into master (5a4d94b) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #382   +/-   ##
=======================================
  Coverage   89.45%   89.45%           
=======================================
  Files          80       80           
  Lines        4192     4192           
=======================================
  Hits         3750     3750           
  Misses        442      442           

Flag	Coverage Δ
unittests	89.45% <100.00%> (ø)

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Impacted Files	Coverage Δ
flash/__about__.py	100.00% <100.00%> (ø)
flash/core/trainer.py	87.50% <100.00%> (ø)

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