class_docstr: VQA v2.0 Open-Ended teacher, which loads the json VQA data and implements the
  ``get`` method to return additional metadata.
docstr: Returns the next example from this dataset after starting to queue up the next
  example.
docstr_tok: ["Returns","the","next","example","from","this","dataset","after","starting","to","queue","up","the","next","example","."]
code: def next_example(self):
      """
      Returns the next example from this dataset after starting to queue up the next
      example.
      """
      ready = None
      # pull up the currently queued example
      if self.example is not None:
          if self.image_mode != "no_image_model":
              # move the image we loaded in the background into the example
              image = self.data_queue.get()
              self.example["image"] = image
          ready = (self.example, self.epochDone)
      # get the next base example: super().next_example() calls self.get()
      self.example, self.epochDone = super().next_example()
      if (
          self.image_mode != "no_image_model"
          and "image_id" in self.example
      ):
          # load the next image in the background
          image_id = self.example["image_id"]
          self.submit_load_request(image_id)
      # Try to return the previously cached example
      if ready is None:
          return self.next_example()
      else:
          return ready
  
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 7 for calling the OeTeacher obj's underlying member method code with example usage: obj.next_example() and returns: self, ready