Hm, that's an interesting question. If you're dealing with a string of lights that has gone out, first check to make sure that there's no damage to the wires or the light bulbs themselves. If you can see a break or a loose wire, you can try to fix it by replacing the bulb or repairing the wire. If the problem is more complex, such as a blown fuse or a malfunctioning power supply, you might need to consult an electrician for help.