add projection layer to roberta encoder

[parmeet]

User may want to additionally project the features from encoder. This PR add support for projecting features to different dimensional space.

[codecov]

Codecov Report

Merging #1451 (157da8b) into main (aea6ad6) will decrease coverage by 0.37%.
The diff coverage is 42.10%.

@@            Coverage Diff             @@
##             main    #1451      +/-   ##
==========================================
- Coverage   86.38%   86.01%   -0.38%     
==========================================
  Files          58       58              
  Lines        2226     2245      +19     
==========================================
+ Hits         1923     1931       +8     
- Misses        303      314      +11     

Impacted Files	Coverage Δ
torchtext/models/roberta/modules.py	78.08% <23.07%> (-4.34%)	⬇️
torchtext/models/roberta/model.py	96.29% <83.33%> (-1.04%)	⬇️

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[Nayef211]

Overall LGTM. It seems like we're getting a lot of code coverage warnings. Should we also add unit tests for the ProjectionLayer class?

[parmeet]

Overall LGTM. It seems like we're getting a lot of code coverage warnings. Should we also add unit tests for the ProjectionLayer class?

Yes, I think it's a good idea. The models tests didn't really touch this part of the code since we are not projecting the encoder output for standard architectures. Though, it would be more like integration/smoke tests instead of unit-test. We also do not have unit tests for other modules as well, but they are covered well through our end-2-end model tests (we call them unit-tests for now, but as @mthrok commented in here, we are going to move them to integration tests as well).

[Nayef211]

Overall LGTM. It seems like we're getting a lot of code coverage warnings. Should we also add unit tests for the ProjectionLayer class?

Yes, I think it's a good idea. The models tests didn't really touch this part of the code since we are not projecting the encoder output for standard architectures. Though, it would be more like integration/smoke tests instead of unit-test. We also do not have unit tests for other modules as well, but they are covered well through our end-2-end model tests (we call them unit-tests for now, but as @mthrok commented in here, we are going to move them to integration tests as well).

Gotcha this makes sense. We can have some followup tasks to add these integrations tests. Stamped!

[joecummings]

@Nayef211 @parmeet Is this still relevant?