code: def num_episodes(self):
      # same as num_examples since only one exchange per episode
      return self.num_examples()
  
imports: from parlai.core.teachers import FixedDialogTeacher
  from parlai.utils.io import PathManager
  from .build import build
  import json
  import os
label_desc: Use image node_id 4 for calling the DefaultTeacher obj's underlying member method code with example usage: obj.num_episodes() and returns: self