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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 as_date(dat):
 """Return the RFC3339 UTC string representation of the given date and time. Args: dat (:py:class:`datetime.date`):
 the object/type to be serialized. Raises: TypeError: when ``o`` is not an instance of ``datetime.date``. Returns: (str) JSON serializable type for the given object. """

    LOGGER.debug('as_date(%s)', dat)

    return strict_rfc3339.timestamp_to_rfc3339_utcoffset(
        calendar.timegm(dat.timetuple()))