code: def get_number_classes(self):
      return len(self.classes)
  
imports: from __future__ import print_function, division, absolute_import
  import csv
  import os
  import os.path
  import tarfile
  from six.moves.urllib.parse import urlparse
  import numpy
  import torch
  import torch.utils.data
  from PIL import Image
  from .None import utils
label_desc: Use image node_id 4 for calling the Voc2007Classification obj's underlying member method code with example usage: obj.get_number_classes() and returns: len