code: def validation_epoch_end(self, outputs):
      self.reporter.update_best_model(np.mean(outputs), self.reward_net)
  
imports: import logging
  from enum import Enum
  from typing import Optional
  import numpy
  import reagent.core.types
  import torch
  from reagent.core.dataclasses import field
  from reagent.models.base import ModelBase
  from reagent.optimizer.union import Optimizer__Union
  from reagent.training.reagent_lightning_module import ReAgentLightningModule
label_desc: Use image node_id 8 for calling the RewardNetTrainer obj's underlying member method code with example usage: obj.validation_epoch_end(outputs) without return types