code: def __init__(self, opt, shared=None):
      opt = copy.deepcopy(opt)
      self.pct_train_exs = opt["light_percent_train_exs"]
      assert 0.0 <= self.pct_train_exs <= 1.0
      opt["parlaidialogteacher_datafile"] = _path(opt)
      if "light_use_speech_prefix" not in opt:
          opt["light_use_speech_prefix"] = True
      super().__init__(opt, shared)
  
imports: from typing import Optional
  from parlai.core.params import ParlaiParser
  from parlai.core.opt import Opt
  from parlai.core.teachers import ParlAIDialogTeacher
  from .build import build
  import copy
  import os
  import random
label_desc: Use image node_id 2 to create a new DefaultTeacher object from inherited base classes: ParlAIDialogTeacher with example: obj = DefaultTeacher(opt, shared)