What is happening in this R code? mlr learners

Question

As part of a course we were given an example of a predictive maintenance (or maybe survival?) analysis. The first part of the code was all about data preprocessing which I understood, I´m just not getting what they do with the data with the following code:

lrn2 = makeImputeWrapper("classif.ranger", classes = list(numeric = imputeMedian()))
lrn3 = makeImputeWrapper("classif.cvglmnet", classes = list(numeric = imputeMedian()))

lrns = list(
  makeLearner("classif.rpart"),
  lrn2,
  lrn3
)

rdesc = makeResampleDesc("LOO", blocking.cv = TRUE)
meas = list(tpr, tnr, mmce)
bmr = benchmark(lrns, task, rdesc, measures = meas)