docstr: Get normalized tokens 
docstr_tok: ["Get","normalized","tokens"]
code: def _get_normalized_tokens(s: str):
      """Get normalized tokens"""
      if not s:
          return []
      return QAMetrics.normalize_answer(s).split()
  
imports: import collections
  import json
  import re
  import string
  import torch
  from tqdm import tqdm
  from nemo.collections.nlp.parts.utils_funcs import tensor2list
  from nemo.utils import logging
label_desc: Use image node_id 5 for calling the QAMetrics obj's underlying member method code with example usage: obj._get_normalized_tokens(s) and returns: QAMetrics, list