[ENH] refactor `_loss_mapping` to tags of metrics, entirely

[fkiraly]

The _loss_mapping looks like it should be refactored to tags of metrics, entirely, in the respective _pkg classes.

Let´s do this! Though we should think about prioritization, or whether this is a "good first issue".

[ParamThakkar123]

@fkiraly Should I take this up ?

[fkiraly]

@ParamThakkar123, if you would like to, sure! This is not a good first issue though, as it requires some familiarity of the framework under the hood.

May I ask you, hence, first, to outline here in the issue the changes that you would make?

[ParamThakkar123]

Hello @fkiraly sorry for the late reply, I forked the repository and made same changes to it I haven't started the pull request yet but this is kind of an outline how I would be making the changes:

ParamThakkar123@579cf5a

Would love any comments on these!

[fkiraly]

Thanks! I thought primarily the LOSSES_BY_PRED_AND_Y_TYPE and the if/else to determine tensor sizes should be moved to tags.

The parameters are for tests, and they could be returned by a method like _get_test_dataloaders_from

[ParamThakkar123]

Sure would make the changes to it.

[ParamThakkar123]

Does this changes look good ? Should I start a PR then maybe you can review it @fkiraly ?

[fkiraly]

@ParamThakkar123, yes, generally speaking, the changes look great! Maybe I'd name the tags differently, but that is more something for when the design is consolidated imo. There is some detail discussion (see what @phoeenniixx said) to be had on teh exact design though.

I would also advise you split the formatting that does not impact losses into a separate PR.

[ParamThakkar123]

Sure @fkiraly , I will make the changes required, I fixed somethings locally and testing them out, once all the tests pass, I will move to fixing the formatting and make a separate pull request for it. Then maybe we can discuss the steps further.