class_docstr: COCO default teacher that expects open-ended descriptions of images.
class_docstr_tok: ["COCO","default","teacher","that","expects","open-ended","descriptions","of","images","."]
code: def num_examples(self):
      if self.version == "2014" or not self.datatype.startswith("test"):
          return len(self.annotation)
      else:
          # For 2017, we only have annotations for the train and val sets,
          # so for the test set we need to determine how many images we have.
          return len(self.test_info["images"])
  
imports: from typing import Optional
  from parlai.core.params import ParlaiParser
  from parlai.core.opt import Opt
  from parlai.core.teachers import FixedDialogTeacher
  from parlai.core.image_featurizers import ImageLoader
  from parlai.utils.io import PathManager
  from .build_2014 import build
  from .build_2014 import buildImage
  from .build_2017 import build
  from .build_2017 import buildImage
  import os
  import json
  import random
label_desc: Use image node_id 4 for calling the DefaultTeacher obj's underlying member method code with example usage: obj.num_examples() and returns: len, len