Fix Gaussian Blur

[AurelienGauffre]

Fix the Gaussian Blur as detailed in #1051. This is just a quick fix example, feel free to reject this PR and write your own clean implementation, although I would love to help if I can.

In particular, this is probably a classical problem, but I am not sure how to handle cleanly the old parameters of GaussianBlur filter as scale or kernel_size that we don't need anymore with this fix : either one can delete these two parameters, but it does not ensure compatibility with older version of Lightly (if a user happened to use the Gaussian Blur function, this will lead to an issue), or one can leave these two unused parameters as is with default values, resulting in a not very clean implementation having useless parameters (current state of the PR).

One important question would be about using the Gaussian Blur either from PIL or from TorchVision.

[Ra1Nik]

Hi, awesome PR, really great finding! I launched the benchmarks running your code. I will have the results tomorrow. I will be back to you as soon as the computation is over!

[Ra1Nik]

I tested the code, and the results are great! Thanks a lot for the finding. You can merge the PR.

We'll stick to PIL images, so we don't need torchvision v0.8.0 as a requirement for lightly. As the next step, we will create an issue to add a deprecation warning, so we will follow your approach. Thanks again!

[guarin]

Thanks a lot!

[codecov]

Codecov Report

Base: 88.79% // Head: 88.79% // Decreases project coverage by -0.01% ⚠️

Coverage data is based on head (f0d9e7a) compared to base (b4fd2b6).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1052      +/-   ##
==========================================
- Coverage   88.79%   88.79%   -0.01%     
==========================================
  Files         107      108       +1     
  Lines        5015     5023       +8     
==========================================
+ Hits         4453     4460       +7     
- Misses        562      563       +1     

Impacted Files	Coverage Δ
lightly/data/collate.py	94.04% <ø> (ø)
lightly/transforms/gaussian_blur.py	100.00% <100.00%> (ø)
lightly/utils/__init__.py	100.00% <0.00%> (ø)
lightly/utils/scheduler.py	81.81% <0.00%> (ø)
lightly/models/utils.py	80.00% <0.00%> (+0.58%)	⬆️

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