code: def _parse_index_file(filename):
      """Parse index file."""
      index = []
      for line in open(filename):
          index.append(int(line.strip()))
      return index
  
imports: from __future__ import absolute_import
  import os, sys
  import pickle
  import warnings
  import networkx
  import numpy
  import scipy.sparse
  from ..None import backend, batch, convert
  from ..convert import from_networkx, graph, to_networkx
  from ..transforms import reorder_graph
  from .dgl_dataset import DGLBuiltinDataset
  from .utils import _get_dgl_url, deprecate_function, deprecate_property, generate_mask_tensor, load_graphs, load_info, makedirs, save_graphs, save_info
label_desc: Use image node_id 3 for calling a global function with example usage: _parse_index_file(filename) and returns: index