Fixing image formatting for test data sets

[kieranfraser]

Description

A number of utility functions are defined in conftest.py for loading default subsets of data (e.g. cifar10 and mnist) which are subsequently used in tests. Some of these methods, depending on the framework used (e.g. PyTorch), change the format of the images from HxWxC to CxHxW, and do so by calling np.reshape, which incorrectly changes the format of the images.

To fix, transpose should be used in place of reshape. This subsequently requires updating any tests which used the incorrect format for images.

Fixes #2101

Type of change

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• Improvement (non-breaking)
• Bug fix (non-breaking)
• New feature (non-breaking)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Testing

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• Test A
• Test B

Test Configuration:

• OS
• Python version
• ART version or commit number
• TensorFlow / Keras / PyTorch / MXNet version

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[codecov-commenter]

Codecov Report

Merging #2104 (997e05d) into dev_1.15.1 (3585836) will decrease coverage by 0.42%.
The diff coverage is n/a.

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@@              Coverage Diff               @@
##           dev_1.15.1    #2104      +/-   ##
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- Coverage       85.61%   85.19%   -0.42%     
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  Files             308      308              
  Lines           27448    27448              
  Branches         5044     5044              
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- Hits            23499    23385     -114     
- Misses           2669     2775     +106     
- Partials         1280     1288       +8     

see 7 files with indirect coverage changes