code: def _samples_set(self, dataset):
      return set(dataset.features)
  
imports: import functools
  import os
  import unittest
  from unittest.mock import MagicMock
  import torch
  from mmf.datasets.base_dataset import BaseDataset
  from mmf.datasets.mmf_dataset_builder import MMFDatasetBuilder
  from mmf.utils.general import get_current_device
  from omegaconf import OmegaConf
label_desc: Use image node_id 6 for calling the TestMMFDatasetBuilder obj's underlying member method code with example usage: obj._samples_set(dataset) and returns: set