docstr: Tests if the data module can be set up in classification mode when no masks are passed.
code: def test_masks_dir_omitted(self, make_data_module):
      """Tests if the data module can be set up in classification mode when no masks are passed."""
      data_module = make_data_module(
          dataset="folder", task="classification", mask_dir=None
      )
      # check if we can retrieve a sample from every subset
      next(iter(data_module.train_dataloader()))
      next(iter(data_module.test_dataloader()))
      next(iter(data_module.val_dataloader()))
  
imports: import os
  import numpy
  import pytest
  from anomalib.config import update_input_size_config
  from anomalib.data import Avenue, BTech, Folder, MVTec, ShanghaiTech, UCSDped, Visa, get_datamodule
  from anomalib.data.utils import DirType
  from anomalib.pre_processing.transforms import Denormalize, ToNumpy
  from tests.helpers.config import get_test_configurable_parameters
  from tests.helpers.dataset import TestDataset, get_dataset_path
label_desc: Use image node_id 6 for calling the TestSubsetSplitting obj's underlying member method code with example usage: obj.test_masks_dir_omitted(make_data_module) without return types