code: def _is_whitespace(char: str) -> bool:
      r"""Checks whether `char` is a whitespace character.
  
      Note: this function is not standard and should be considered for BERT
      tokenization only. See the comments for more details.
      """
      # \t, \n, and \r are technically control characters but we treat them
      # as whitespace since they are generally considered as such.
      if char in (" ", "\t", "\n", "\r"):
          return True
      cat = unicodedata.category(char)
      if cat == "Zs":
          return True
      return False
  
file_path: texar/texar/tf/data/tokenizers/bert_tokenizer_utils.py
imports: from typing import Dict, List, Optional
  import collections
  import unicodedata
label_desc: Use image node_id 3 for calling a global function with example usage: _is_whitespace(char) and returns: False, True, True