Return the first net_interface.%d.ip for a system in a public/private network.

def __getIP(self, public):
        """Return the first net_interface.%d.ip for a system in a public/private network."""

        maybeNot = (lambda x: x) if public else (lambda x: not x)
        nets_id = [net.id for net in self.networks if maybeNot(net.isPublic())]
        for s in self.systems:
            i = 0
            while True:
                value = s.getValue("net_interface.%d.connection" % i)
                if not value:
                    break
                if value in nets_id:
                    ip = s.getValue("net_interface.%d.ip" % i)
                    if ip:
                        return ip
                i += 1
        return None