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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(value):
 """ Return the timestamp of a datetime.datetime object. :param value: a datetime object :type value: datetime.datetime :return: the timestamp :rtype: str """

    value = value if timezone.is_naive(value) else timezone.localtime(value)
    return value.strftime(settings.DATE_FORMAT)