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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 add_range(self, name, start=None, end=None):
 """ Adds a date range to the given facet. :param str name: The name by which the results within the range can be accessed :param str start: Lower date range. Should be in RFC 3339 format :param str end: Upper date range. :return: The `DateFacet` object, so calls to this method may be chained """

        self._ranges.append(_mk_range_bucket(name, 'start', 'end', start, end))
        return self