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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 timestamp(self, value):
 """ The local time when the message was written. Must follow the format 'Mmm DD HH:MM:SS'. If the day of the month is less than 10, then it MUST be represented as a space and then the number. """

        if not self._timestamp_is_valid(value):
            value = self._calculate_current_timestamp()
        self._timestamp = value