[RFC] Add missing names to pl_bolts/datasets/__init__.py

[akihironitta]

What does this PR do?

It seems strange to me that pl_bolts/datasets/__init__.py has only dummy datasets. This PR adds missing items to the init.py to make all dataset classes (and functions) available right under pl_bolts.datasets.

In short, this PR enables:

from pl_bolts.datasets import BinaryMNIST  # This doesn't work on the current master branch.

where we have to write on the master branch:

from pl_bolts.datasets.mnist_dataset import BinaryMNIST

I'd like to merge this PR since this change can make the tests for imports in #428 easier.
If not having dataset classes in pl_bolts/datasets/__init__.py on purpose, please just close this PR...

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[codecov]

Codecov Report

Merging #493 (a3a9f00) into master (6b2136b) will decrease coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #493      +/-   ##
==========================================
- Coverage   77.53%   77.51%   -0.03%     
==========================================
  Files         114      114              
  Lines        6664     6670       +6     
==========================================
+ Hits         5167     5170       +3     
- Misses       1497     1500       +3     

Flag	Coverage Δ
cpu	25.87% <100.00%> (+0.06%)	⬆️
pytest	25.87% <100.00%> (+0.06%)	⬆️
unittests	76.98% <100.00%> (-0.03%)	⬇️

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

Impacted Files	Coverage Δ
pl_bolts/datasets/__init__.py	100.00% <100.00%> (ø)
pl_bolts/datasets/cifar10_dataset.py	70.96% <100.00%> (ø)
pl_bolts/models/self_supervised/amdim/datasets.py	56.89% <100.00%> (-0.74%)	⬇️
...l_bolts/models/rl/vanilla_policy_gradient_model.py	92.79% <0.00%> (-2.71%)	⬇️

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[akihironitta]

@Borda Do you find this change reasonable? If so, I'll move forward by adding some changes to the docs in this PR.

[Borda]

@Borda Do you find this change reasonable? If so, I'll move forward by adding some changes to the docs in this PR.

not sure how this helps, would it work if you have not installed all packages needed for other datamodules?

[akihironitta]

@Borda Do you find this change reasonable? If so, I'll move forward by adding some changes to the docs in this PR.

not sure how this helps, would it work if you have not installed all packages needed for other datamodules?

Yes. Before #338, ModuleNotFoundError was raised as soon as modules cannot find optional packages, which led to importing problems in the past, but #338 replaced the ModuleNotFoundError with warnings, so it should work without any optional packages installed.
related diff: https://github.com/PyTorchLightning/pytorch-lightning-bolts/pull/338/files#diff-30bd8712b62d3a1204186cc19600041c03996ddd4998d1fbe567843d010c7e69

Shall I keep going then?

[akihironitta]

@Borda @ananyahjha93 Would love to hear your thoughts on this.

[Borda]

@akihironitta I have added nb of workers but not sure if it is the reason for failing the test...

[akihironitta]

@Borda I guess this is ready to go once the tests pass in CI.