code: def num_classes(self):
      return self._num_classes
  
imports: import os
  import json
  import glob
  import h5py
  from PIL import Image, ImageOps
  from torchmeta.utils.data import Dataset, ClassDataset, CombinationMetaDataset
  from torchvision.datasets.utils import list_dir, download_url
  from torchmeta.datasets.utils import get_asset
label_desc: Use image node_id 3 for calling the OmniglotClassDataset obj's underlying member method code with example usage: obj.num_classes() and returns: self