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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def format_stackdriver_json(record, message):
 """Helper to format a LogRecord in in Stackdriver fluentd format. :rtype: str :returns: JSON str to be written to the log file. """

    subsecond, second = math.modf(record.created)

    payload = {
        "message": message,
        "timestamp": {"seconds": int(second), "nanos": int(subsecond * 1e9)},
        "thread": record.thread,
        "severity": record.levelname,
    }

    return json.dumps(payload)