Replacing model with predictions data about what-if-tool

[jameswex]

There are two approaches that would work:

1. Have the datapoints contain the prediction outputs directly with specially named fields. See the note at the bottom of https://pair-code.github.io/what-if-tool/learn/tutorials/notebooks/

2. Write a custom prediction function that looks like the pre-calculated prediction data for each example instead of having it call the model (https://pair-code.github.io/what-if-tool/learn/tutorials/custom-prediction/)

Note that in either of these cases, some features (partial dependence plots, for example) won't work as expected as there is no way to get predictions for newly created datapoints.