code: def num_examples(self):
      return len(self.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 3 for calling the DefaultTeacher obj's underlying member method code with example usage: obj.num_examples() and returns: len