def _is_whitespace(char):
    """Checks whether `chars` is a whitespace character."""
    # \t, \n, and \r are technically contorl characters but we treat them
    # as whitespace since they are generally considered as such.
    if char == ' ' or char == '\t' or char == '\n' or char == '\r':
        return True
    cat = unicodedata.category(char)
    if cat == 'Zs':
        return True
    return False
Checks whether `chars` is a whitespace character.
bert_tokenizer.py