Simplify post-prediction schema info to make user-friendly prediction's info such as list of ranked predicted labels/categories

[CESARDELATORRE]

CONTEXT:

In this PR (and probably, available in 0.10), we're allowing the user to get some schema info after predicting:

#2250

That way a user can get, for example, get the list of the predicted labels in a multi-class classification and related that to the list/array of scores.

That's very useful for business cases where you want to automatically predict/assign a product to multiple categories, for example, instead of predicting a single category/label.

However, the current user's code needs to be like the following, using not user-friendly types such as VBuffer, etc.:

            // Slot names on top of Score column represent original labels for i-th value in Score array.
            VBuffer<ReadOnlyMemory<char>> slotNames = default;
            engine.OutputSchema[nameof(IrisPrediction.Score)].GetSlotNames(ref slotNames);
            // Key names represent original values for PredictedLabel column.
            VBuffer<ReadOnlyMemory<char>> keys = default;
            engine.OutputSchema[nameof(IrisPrediction.PredictedLabel)].GetKeyValues(ref keys);

            Assert.True(slotNames.GetItemOrDefault(0).ToString() == "Iris-setosa");
            Assert.True(slotNames.GetItemOrDefault(1).ToString() == "Iris-versicolor");
            Assert.True(slotNames.GetItemOrDefault(2).ToString() == "Iris-virginica");

REQUEST:

The ask is to simplify it and provide types and simpler API with user-friendly data-types that are familiar for regular .NET developers.

Also, a more straightforward way to relate the list of labels with their related scores. Maybe returning a single array/list with both concepts coming along (labels-scores) instead of separated arrays/lists?

---

Related info

This topic is related with this original issue, too:
Multi-class classification returning ranked list of possible labels): #2233

[prathyusha12345]

@Ivanidzo4ka Is anyone working on simplifying this code for 0.11? Or not yet?
Thanks,

[Ivanidzo4ka]

@prathyusha12345
I know we have proposal regarding Metadata itself: #2622 but I didn't have time to look on it yet.

[aljones007]

Is anyone looking into this yet? Just wondering if there is a simple way of getting the multi-labels out. Thanks.

[gvashishtha]

@aljones007 it is in our backlog, and we hope to make some progress on this soon.