Helper class for NaiveCredal Classifier, used to store crossing points and minimizing tuples; it is used
when missing data in the NonMar part of the testing instances.
Index of NonMar features positions in the current
testing set (position might change during CV, as different variables can get discretized into a single bin)
Index of NonMar features positions in the current
training set (position might change during CV, as different variables can get discretized into a single bin)