def clean_semver(cls, version_spec):
        return re.sub(r"([<>=~])\s+?v?", "\\1", version_spec, re.IGNORECASE)
def peirce_skill_score(self):
        """
        Multiclass Peirce Skill Score (also Hanssen and Kuipers score, True Skill Score)
        """
        n = float(self.table.sum())
        nf = self.table.sum(axis=1)
        no = self.table.sum(axis=0)
        correct = float(self.table.trace())
        return (correct / n - (nf * no).sum() / n ** 2) / (1 - (no * no).sum() / n ** 2)