Recsys losses

[sergunya17]

Before submitting (checklist)

• Was this discussed/approved via a Github issue? (no need for typos and docs improvements)
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• Did you make sure to update the docs? We use Google format for all the methods and classes.
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• Did you write any new necessary tests?
• Did you check that your code passes the unit tests pytest . ?
• Did you add your new functionality to the docs?
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Description

Added losses:

• AdaptiveHingeLoss
• BPRLoss
• HingeLoss
• LogisticLoss
• WARPLoss

Based on #1253, #1255

Type of Change

• Examples / docs / tutorials / contributors update
• Bug fix (non-breaking change which fixes an issue)
• Improvement (non-breaking change which improves an existing feature)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

[pep8speaks]

Hello @sergunya17! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

There are currently no PEP 8 issues detected in this Pull Request. Cheers! 🍻

Comment last updated at 2021-08-09 22:13:19 UTC

[Scitator]

a few questions here:

1. do we really need Pointwise, PairwiseLoss and ListWiseLoss abstractions?
2. could you please add usage examples for each implemented criterion? I hope, it would be much easier to understand them in this way :)

[mergify]

This pull request is now in conflicts. @sergunya17, could you fix it? 🙏