Resolve: 'DummyExperiment' object does not support item assignment

[lucmos]

What does this PR do?

Add the __setitem__ method to the DummyExperiment

The new Neptune API use a dict-like interface to log metrics/parameters, thus the DummyExperiment must have a __setitem__ implemented otherwise an error is raised:

'DummyExperiment' object does not support item assignment

Does your PR introduce any breaking changes? If yes, please list them.

None

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[justusschock]

@lucmos thanks for your PR: do you have a concrete usecase where you encounter this? Ideally with a reproducible minimal example? Ideally we would discuss such things in an issue (we appreciate proposed solutions there very much) before sending a PR and then linking that issue here so that everybody can look up the reason for this change :)

I don't see how this could hurt, but reluctant to approve it without more information :)

Also a test and a changelog entry would be required

[lucmos]

Hello @justusschock, thanks for the quick response! :)
Sure, I skipped the changelog because I considered it an "internal minor change" and the change is quite minimal. I will add the relative test.

---

The use case is specific to Neptune users who can log with the dict-like syntax:

e.g.

logger.experiment[keyname] = keyvalue

The DummyExperiment is used to dummi-fy the experiment (e.g. in ddp strategies), thus it should support the item assignment in codebases that use the new neptune API.

If you prefer I can make the colab mwe though