GetReviewsSummary.
        [Preview API] Returns a summary of the reviews
        :param str pub_name: Name of the publisher who published the extension
        :param str ext_name: Name of the extension
        :param datetime before_date: Use if you want to fetch summary of reviews older than the specified date, defaults to null
        :param datetime after_date: Use if you want to fetch summary of reviews newer than the specified date, defaults to null
        :rtype: :class:`<ReviewSummary> <azure.devops.v5_0.gallery.models.ReviewSummary>`

def get_reviews_summary(self, pub_name, ext_name, before_date=None, after_date=None):
        """GetReviewsSummary.
        [Preview API] Returns a summary of the reviews
        :param str pub_name: Name of the publisher who published the extension
        :param str ext_name: Name of the extension
        :param datetime before_date: Use if you want to fetch summary of reviews older than the specified date, defaults to null
        :param datetime after_date: Use if you want to fetch summary of reviews newer than the specified date, defaults to null
        :rtype: :class:`<ReviewSummary> <azure.devops.v5_0.gallery.models.ReviewSummary>`
        """
        route_values = {}
        if pub_name is not None:
            route_values['pubName'] = self._serialize.url('pub_name', pub_name, 'str')
        if ext_name is not None:
            route_values['extName'] = self._serialize.url('ext_name', ext_name, 'str')
        query_parameters = {}
        if before_date is not None:
            query_parameters['beforeDate'] = self._serialize.query('before_date', before_date, 'iso-8601')
        if after_date is not None:
            query_parameters['afterDate'] = self._serialize.query('after_date', after_date, 'iso-8601')
        response = self._send(http_method='GET',
                              location_id='b7b44e21-209e-48f0-ae78-04727fc37d77',
                              version='5.0-preview.1',
                              route_values=route_values,
                              query_parameters=query_parameters)
        return self._deserialize('ReviewSummary', response)