def previous(self, step=1):
        ip_copy = self.__class__('%s/%d' % (self.network, self.prefixlen),
            self._module.version)
        ip_copy -= step
        return ip_copy
:param step: the number of IP subnets between this `IPNetwork` object
dataset/ETHPy150Open drkjam/netaddr/netaddr/ip/__init__.py/IPNetwork.previous