code: def _add_masked_question(self, sample_info, current_sample):
      question = sample_info["question_str"]
      random_answer = random.choice(sample_info["all_answers"])
  
      processed = self.masked_token_processor(
          {
              "text_a": question,
              "text_b": random_answer,
              "is_correct": -1,
          }
      )
  
      processed.pop("tokens")
      current_sample.update(processed)
  
      return current_sample
  
imports: import random
  from mmf.common.sample import Sample
  from mmf.datasets.builders.vqa2.dataset import VQA2Dataset
label_desc: Use image node_id 3 for calling the MaskedVQA2Dataset obj's underlying member method code with example usage: obj._add_masked_question(sample_info, current_sample) and returns: current_sample