class_docstr: Test vis
code: def test_vis(self):
      image_folder_sample_show(
          root=self.root_dir, rows=1, cols=1, img_size=20
      )
      self.assertEqual(len(list(self.class1_path.iterdir())), 1)
  
imports: import unittest
  import torch
  from pathlib import Path
  from torchvision import transforms
  from torchvision.models import resnet18
  from towhee.utils.pil_utils import PILImage
  from towhee.utils.matplotlib_utils import matplotlib
  from towhee.trainer.utils.plot_utils import image_folder_sample_show, image_folder_statistic, show_transform, plot_lrs_for_config, plot_lrs_for_scheduler, interpret_image_classification
  from towhee.trainer.training_config import TrainingConfig
  from torch import nn
  from torch.optim.lr_scheduler import StepLR
label_desc: Use image node_id 2 for calling the TestVisualizationUtil obj's underlying member method code with example usage: obj.test_vis() without return types