class_docstr: Paraphrase problem.
code: def _get_captions(self, ms_coco_path):
      caption_file = io.open(ms_coco_path)
      caption_json = json.load(caption_file)
      annotations = caption_json["annotations"]
      captions_for_image = collections.defaultdict(list)
  
      for annotation in annotations:
          image_id = annotation["image_id"]
          captions_for_image[image_id].append(annotation["caption"])
  
      captions = list(captions_for_image.values())
      return captions
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import collections
  import io
  import json
  import os
  import zipfile
  from tensor2tensor.data_generators import generator_utils
  from tensor2tensor.data_generators import problem
  from tensor2tensor.data_generators import text_problems
  from tensor2tensor.utils import registry
  import tensorflow.compat.v1
label_desc: Use image node_id 6 for calling the ParaphraseGenerationMsCocoProblem obj's underlying member method code with example usage: obj._get_captions(ms_coco_path) and returns: captions