code: def num_classes(self) -> int:
      return self.__meta__["num_classes"]
  
imports: from typing import Optional, Union, Dict
  import os
  import shutil
  import os.path
  import torch
  import numpy
  from ogb.utils.url import decide_download, download_url, extract_zip, makedirs
  from ogb.lsc.utils import split_test
label_desc: Use image node_id 8 for calling the MAG240MDataset obj's underlying member method code with example usage: obj.num_classes() and returns: self