Get the bare Learner without the CPOs that were previously added.
It is still possible for the result to be a wrapped learner, e.g. a TuningWrapper wrapped learner. It is also possible that below the tuning wrapper, there are more CPOs. These can and will not be removed.
This function is complementary to getLearnerCPO.
getLearnerBare(learner)[Learner]
The learner to strip.
[Learner]. The learner without attached CPOs.
Other CPOLearner related: CPOLearner,
  attachCPO, getLearnerCPO