def delete(self, doc):
        if doc.id is None:
            raise DatabaseException('Document does not have id')
        if doc.sid is None:
            try:
                rs = self.db.docs.remove({'id': doc.id}, safe=True)
                assert rs['n'] == 1
            except Exception as e:
                raise DatabaseException(e)
            return None
        doc.data = None
        return self.update(doc)
def main():
    # Contingency Table from Wilks (2011) Table 8.3
    table = np.array([[50, 91, 71],
                      [47, 2364, 170],
                      [54, 205, 3288]])
    mct = MulticlassContingencyTable(table, n_classes=table.shape[0],
                                     class_names=np.arange(table.shape[0]).astype(str))
    print(mct.peirce_skill_score())
    print(mct.gerrity_score())