refactor: cb_explore_adf_bag.cc make_reduction_learner (#3016)

* refactor: cb_explore_adf_bag.cc

* reformat

* remove comment

* reformat

Co-authored-by: root <root@griffinbassman.localdomain>

vowpalwabbit/cb_explore_adf_bag.cc

@@ -12,6 +12,7 @@
 #include "gen_cs_example.h"
 #include "cb_explore.h"
 #include "explore.h"
+#include "label_parser.h"
 #include <vector>
 #include <algorithm>
 #include <cmath>
@@ -178,16 +179,18 @@ VW::LEARNER::base_learner* setup(VW::config::options_i& options, vw& all)
   bool with_metrics = options.was_supplied("extra_metrics");
 
   using explore_type = cb_explore_adf_base<cb_explore_adf_bag>;
-  auto data = scoped_calloc_or_throw<explore_type>(
-      with_metrics, epsilon, bag_size, greedify, first_only, all.get_random_state());
-
-  VW::LEARNER::learner<explore_type, multi_ex>& l = VW::LEARNER::init_learner(data, base, explore_type::learn,
-      explore_type::predict, problem_multiplier, prediction_type_t::action_probs, all.get_setupfn_name(setup) + "-bag");
-
-  l.set_finish_example(finish_bag_example);
-  l.set_print_example(print_bag_example);
-  l.set_persist_metrics(explore_type::persist_metrics);
-  return make_base(l);
+  auto data =
+      VW::make_unique<explore_type>(with_metrics, epsilon, bag_size, greedify, first_only, all.get_random_state());
+  auto* l = make_reduction_learner(
+      std::move(data), base, explore_type::learn, explore_type::predict, all.get_setupfn_name(setup) + "-bag")
+                .set_params_per_weight(problem_multiplier)
+                .set_prediction_type(prediction_type_t::action_probs)
+                .set_label_type(label_type_t::cb)
+                .set_finish_example(finish_bag_example)
+                .set_print_example(print_bag_example)
+                .set_persist_metrics(explore_type::persist_metrics)
+                .build();
+  return make_base(*l);
 }
 
 }  // namespace bag