Normalizes the string using tokenizer.encode.

  Args:
    raw_str: the input string

  Returns:
   A string which is ready to be tokenized using split()

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)))