code: def _normalize_string(raw_str):
      """Normalizes the string using tokenizer.encode.
  
      Args:
        raw_str: the input string
  
      Returns:
       A string which is ready to be tokenized using split()
      """
      return " ".join(
          token.strip()
          for token in tokenizer.encode(
              text_encoder.native_to_unicode(raw_str)
          )
      )
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import collections
  import os
  import shutil
  import tarfile
  import requests
  import six
  from tensor2tensor.data_generators import problem
  from tensor2tensor.data_generators import text_encoder
  from tensor2tensor.data_generators import text_problems
  from tensor2tensor.data_generators import tokenizer
  from tensor2tensor.layers import modalities
  from tensor2tensor.utils import metrics
  from tensor2tensor.utils import registry
  import tensorflow.compat.v1
label_desc: Use image node_id 1 for calling a global function with example usage: _normalize_string(raw_str) and returns: str