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.
        """
        if self.updated:
            return 0

        res = super(BipartiteGraph, self).update()
        self.updated = True
        return res