code: def _get_image_id(self, idx):
      return self.annotation_db[idx][_CONSTANTS["image_id_key"]]
  
file_path: mmf/mmf/datasets/builders/visual_genome/dataset.py
imports: import copy
  import json
  import torch
  from mmf.common.sample import Sample, SampleList
  from mmf.datasets.builders.vqa2 import VQA2Dataset
  from mmf.datasets.databases.scene_graph_database import SceneGraphDatabase
label_desc: Use image node_id 3 for calling the VisualGenomeDataset obj's underlying member method code with example usage: obj._get_image_id(idx) and returns: self