Anomalous score of this reviewer.

        Initial anomalous score is :math:`1 / |R|`
        where :math:`R` is a set of reviewers.

def anomalous_score(self):
        """Anomalous score of this reviewer.

        Initial anomalous score is :math:`1 / |R|`
        where :math:`R` is a set of reviewers.
        """
        return self._anomalous if self._anomalous else 1. / len(self._graph.reviewers)