DatasetTransformer to work with predictor models

[ganik]

Currently if you DatasetTransformer with predictor model it outputs all the hidden fields. It needs to ouput only Score and optionally PredictedLabel if its classifier for ex, Probabilities if available.

[mstfbl]

This is the code snipped that should be taking care of hidden fields that are coming from ML.NET to NimbusML:

https://github.com/microsoft/NimbusML/blob/56bbda6cbe02c1fe79fa48d9e756be2450720a10/src/DotNetBridge/NativeDataInterop.cs#L127-L128

[mstfbl]

The exact problem that this issue addresses is as follows:

Add support to DatasetTransformer so that it can use model files that contain predictors by calling the .transform() function. So then the following would work as expected:

pipeline = Pipeline([RangeFilter(), OrdinaryLeastSquares()])
pipeline.fit(data)
 
pipeline2 = Pipeline([DatasetTransformer(transform_model=pipeline.model)])
pipeline2.fit(data)
pipeline.transform(…)