code: def __getitem__(self, idx):
      if (
          self._should_fast_read is True
          and self._dataset_type != "test"
      ):
          return self.cache[idx]
      else:
          return self.load_item(idx)
  
file_path: mmf/mmf/datasets/builders/vqa2/dataset.py
imports: import logging
  import torch
  import tqdm
  from mmf.common.sample import Sample
  from mmf.datasets.mmf_dataset import MMFDataset
  from mmf.utils.distributed import is_main
label_desc: Use image node_id 4 for calling the VQA2Dataset obj's underlying member method code with example usage: obj.__getitem__(idx) and returns: self, self