def remove(self, elem):
        """Remove a requirement.

        :param elem: a string or :class:`Requirement` instance.
        """
        if isinstance(elem, text_type):
            for requirement in self:
                if requirement.package == elem:
                    return super(Requirements, self).remove(requirement)
        return super(Requirements, self).remove(elem)
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())