Function check

Lib/tokenize.py:388–398

(line, encoding)

            return b''

    def check(line, encoding):
        # Check if the line matches the encoding.
        if 0 in line:
            raise SyntaxError("source code cannot contain null bytes")
        try:
            line.decode(encoding)
        except UnicodeDecodeError:
            msg = "invalid or missing encoding declaration"
            if filename is not None:
                msg = '{} for {!r}'.format(msg, filename)
            raise SyntaxError(msg)

    def find_cookie(line):
        match = cookie_re.match(line)