def _clean_text(self, text):
        """Performs invalid character removal and whitespace cleanup on text."""
        output = []
        for char in text:
            cp = ord(char)
            if cp == 0 or cp == 0xfffd or _is_control(char):
                continue
            if _is_whitespace(char):
                output.append(' ')
            else:
                output.append(char)
        return ''.join(output)
Performs invalid character removal and whitespace cleanup on text.
bert_tokenizer.py