code: def get_reviews_summary(self, pub_name, ext_name, before_date=None, after_date=None):
          
          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)
docs: 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>`