code: def test_keep_only_last_best_without_save_best_only(self):
      with self.assertRaises(ValueError):
          PeriodicEpochSave(
              self.save_filename,
              monitor="val_loss",
              verbose=True,
              save_best_only=False,
              keep_only_last_best=True,
          )
  
      with self.assertRaises(ValueError):
          PeriodicEpochSave(
              self.save_filename,
              monitor="val_loss",
              verbose=True,
              keep_only_last_best=True,
          )
  
imports: import os
  import unittest
  from tempfile import TemporaryDirectory
  from typing import IO, Dict
  from unittest import TestCase
  from unittest.mock import MagicMock, call
  import torch
  import torch.nn
  from poutyne import Model, PeriodicSaveCallback, PeriodicSaveLambda
  from tests.framework.tools import some_data_generator
label_desc: Use image node_id 17 for calling the PeriodicSaveTest obj's underlying member method code with example usage: obj.test_keep_only_last_best_without_save_best_only() without return types