code: def on_train_end(self, logs: Dict):
      super().on_train_end(logs)
      for layer in self.layers:
          self.csvfiles[layer].close()
  
imports: import csv
  import os
  from typing import Dict, List, Optional, TextIO, Union
  import torch
  from poutyne.framework.callbacks._utils import atomic_lambda_save
  from poutyne.framework.callbacks.callbacks import Callback
label_desc: Use image node_id 4 for calling the CSVGradientLogger obj's underlying member method code with example usage: obj.on_train_end(logs) without return types