raise clear error for module not available

[aniketmaurya]

What does this PR do?

Fixes #1422 #1423. This PR:

• Adds @requires("kornia") decorator to image segmentation input transform code for better coverage and clearer error.
• Since Audio Classification uses torchvision, a requires decorator for torchvision is also added in the relevant file.

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• Did you make sure your PR does only one thing, instead of bundling different changes together?
• Did you make sure to update the documentation with your changes?
• Did you write any new necessary tests? [not needed for typos/docs]
• Did you verify new and existing tests pass locally with your changes?
• If you made a notable change (that affects users), did you update the CHANGELOG?

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[codecov]

Codecov Report

Merging #1425 (c054bf0) into master (c892d69) will decrease coverage by 7.77%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1425      +/-   ##
==========================================
- Coverage   92.89%   85.12%   -7.78%     
==========================================
  Files         286      286              
  Lines       12870    12874       +4     
==========================================
- Hits        11956    10959     -997     
- Misses        914     1915    +1001     

Flag	Coverage Δ
unittests	85.12% <100.00%> (-7.78%)	⬇️

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

Impacted Files	Coverage Δ
flash/audio/classification/input_transform.py	92.59% <100.00%> (+0.28%)	⬆️
flash/core/utilities/imports.py	91.42% <100.00%> (ø)
flash/image/segmentation/input_transform.py	94.59% <100.00%> (+0.47%)	⬆️
...lash/image/embedding/vissl/transforms/utilities.py	15.15% <0.00%> (-84.85%)	⬇️
flash/image/embedding/heads/vissl_heads.py	35.29% <0.00%> (-64.71%)	⬇️
flash/image/embedding/losses/vissl_losses.py	37.50% <0.00%> (-62.50%)	⬇️
flash/image/embedding/vissl/adapter.py	31.63% <0.00%> (-62.25%)	⬇️
flash/image/detection/input.py	38.88% <0.00%> (-61.12%)	⬇️
...age/face_detection/backbones/fastface_backbones.py	42.10% <0.00%> (-57.90%)	⬇️
flash/image/face_detection/model.py	36.84% <0.00%> (-55.27%)	⬇️
... and 57 more

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[krshrimali]

Thank you, @aniketmaurya for this PR! LGTM 🔥 A suggestion and a question:

1. Let's also add torchvision requirement to datatype_audio.txt file, since we need it for audio classification. Can you please do this in this PR?
2. Question: just cross-checking, did you make sure that a clearer error is raised if kornia is not installed and a user attempts to run this example?

Also, I've modified the PR description for future reference, just in case anyone hops on this for any reason! :) Hope that sounds good to you.

[aniketmaurya]

Thank you for reviewing the PR and suggestions @krshrimali 😄 !
I have added torchvision to audio requirements and also cross-checked the error message when Kornia is not uninstalled. The error message clearly states that Konia is not installed 👇🏻

ModuleNotFoundError: Required dependencies not available. Please run: pip install 'kornia'

[krshrimali]

@aniketmaurya - Sounds great, thank you so much! However, I can't see any commit after your comment. Did you forget to push the changes for requirements? ;)

[aniketmaurya]

Hi @krshrimali, yeah sorry I forgot to push it earlier. I've updated the PR just now! 😅

[krshrimali]

Update: added CHANGELOG entries! cc: @ethanwharris - if you can merge this whenever you are back! :)

[ethanwharris]

LGTM, just small suggestions to require lightning-flash[image] or lightning-flash[audio] rather than the libraries themselves