class_docstr: VQA v2.0 Open-Ended teacher, which inherits from OeTeacher and gives access to the
  multiple choice answer.
code: def act(self):
      action = super().act()
  
      if not self.datatype.startswith("test"):
          anno = self.annotation["annotations"][self.episode_idx]
          self.mclabel = [anno["multiple_choice_answer"]]
  
      if self.datatype.startswith("train"):
          action["mc_label"] = self.mclabel
  
      return action
  
imports: from parlai.utils.io import PathManager
  from parlai.core.teachers import FixedDialogTeacher
  from parlai.core.image_featurizers import ImageLoader
  from .build import build
  from parlai.tasks.coco_caption.build_2014 import buildImage
  from parlai.tasks.coco_caption.build_2015 import buildImage
  import json
  import os
label_desc: Use image node_id 1 for calling the AllTeacher obj's underlying member method code with example usage: obj.act() and returns: action