Update reviewers' anomalous scores and products' summaries.

        Returns:
          maximum absolute difference between old summary and new one, and
          old anomalous score and new one.

def update(self):
        """Update reviewers' anomalous scores and products' summaries.

        Returns:
          maximum absolute difference between old summary and new one, and
          old anomalous score and new one.
        """
        w = self._weight_generator(self.reviewers)
        diff_p = max(p.update_summary(w) for p in self.products)
        diff_a = max(r.update_anomalous_score() for r in self.reviewers)
        return max(diff_p, diff_a)