Tries to find custom data from the old logging record.  The
        return value is a dictionary that is merged with the log record
        extra dictionaries.

def find_extra(self, record):
        """Tries to find custom data from the old logging record.  The
        return value is a dictionary that is merged with the log record
        extra dictionaries.
        """
        rv = vars(record).copy()
        for key in ('name', 'msg', 'args', 'levelname', 'levelno',
                    'pathname', 'filename', 'module', 'exc_info',
                    'exc_text', 'lineno', 'funcName', 'created',
                    'msecs', 'relativeCreated', 'thread', 'threadName',
                    'processName', 'process'):
            rv.pop(key, None)
        return rv