code: def update_best_model(self, loss: float, model: ModelBase):
      if loss < self.best_model_loss:
          self.best_model_loss = loss
          self.best_model = copy.deepcopy(model)
  
file_path: ReAgent/reagent/reporting/reward_network_reporter.py
imports: import copy
  import logging
  from reagent.core import aggregators
  from reagent.core.observers import IntervalAggregatingObserver
  from reagent.models.base import ModelBase
  from reagent.reporting.reporter_base import ReporterBase
  from reagent.training.reward_network_trainer import LossFunction
label_desc: Use image node_id 4 for calling the RewardNetworkReporter obj's underlying member method code with example usage: obj.update_best_model(loss, model) without return types