docstr:     Calculate the number of classes of the output label.
  Return:
      int: the number of classes
docstr_tok: ["Calculate","the","number","of","classes","of","the","output","label",".","Return",":","int",":","the","number","of","classes"]
code: def num_classes(self):
      """
          Calculate the number of classes of the output label.
      Return:
          int: the number of classes
      """
  
      return self._nb_classes
  
file_path: AdvBox/adversarialbox/models/mxnet.py
imports: from __future__ import absolute_import
  import numpy
  import os
  from .base import Model
  import logging
label_desc: Use image node_id 3 for calling the MxNetModel obj's underlying member method code with example usage: obj.num_classes() and returns: self