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 object_id(self):
        return ("ip-path-mtu-%d-%s-%d" % (self.table_id,
                                          self.nh,
                                          self.pmtu))