def load(self, filename, create_if_missing=True):
        filename = Path(filename)
        if not filename.exists() and create_if_missing:
            self.load_pip_requirements()
            with filename.open("w") as f:
                f.write(yaml.dump(self.serialized, default_flow_style=False,
                                  encoding=None))
            self.filename = filename
            return self.save(filename)
        with filename.open() as f:
            for group, requirements in yaml.load(f.read()).items():
                for requirement in requirements:
                    self[group].add(Requirement.coerce(requirement))
        self.filename = filename
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)