code: def tokenize_and_index(self, sentence):
      inds = [self.word2idx(w) for w in tokenize(sentence)]
      return inds
  
imports: import os
  import re
  from collections import Counter
  from itertools import chain
  import torch
  from mmf.common.registry import registry
  from mmf.utils.file_io import PathManager
  from mmf.utils.general import get_absolute_path
label_desc: Use image node_id 9 for calling the VocabDict obj's underlying member method code with example usage: obj.tokenize_and_index(sentence) and returns: inds