class_docstr: Trainer for Seq2Reward
class_docstr_tok: ["Trainer","for","Seq2Reward"]
code: def validation_step(
      self, batch: rlt.MemoryNetworkInput, batch_idx: int
  ):
      detached_mse_loss = self.get_mse_loss(batch).cpu().detach().item()
  
      detached_step_entropy_loss = (
          self.get_step_entropy_loss(batch).cpu().detach().item()
      )
  
      state_first_step = batch.state.float_features[0]
      # shape: batch_size, action_dim
      q_values_all_action_all_data = get_Q(
          self.seq2reward_network,
          state_first_step,
          self.all_permut,
      ).cpu()
      q_values = q_values_all_action_all_data.mean(0).tolist()
  
      action_distribution = torch.bincount(
          torch.argmax(q_values_all_action_all_data, dim=1),
          minlength=len(self.params.action_names),
      )
      # normalize
      action_distribution = (
          action_distribution.float() / torch.sum(action_distribution)
      ).tolist()
  
      self.reporter.log(
          eval_mse_loss=detached_mse_loss,
          eval_step_entropy_loss=detached_step_entropy_loss,
          eval_q_values=[q_values],
          eval_action_distribution=[action_distribution],
      )
      return (
          detached_mse_loss,
          detached_step_entropy_loss,
          q_values,
          action_distribution,
      )
  
imports: import logging
  import reagent.core.types
  import torch
  import torch.nn
  import torch.nn.functional
  from reagent.core.parameters import Seq2RewardTrainerParameters
  from reagent.models.fully_connected_network import FullyConnectedNetwork
  from reagent.models.seq2reward_model import Seq2RewardNetwork
  from reagent.training.reagent_lightning_module import ReAgentLightningModule
  from reagent.training.utils import gen_permutations
label_desc: Use image node_id 4 for calling the Seq2RewardTrainer obj's underlying member method code with example usage: obj.validation_step(batch, batch_idx) and returns: detached_mse_loss,  detached_step_entropy_loss,  q_values,  action_distribution