This is an exercise that we made up to try and bridge the gap between other exercises and Christmas Tree.
This is accompanied by this video: https://www.youtube.com/watch?v=PhCEgCPrmBE
Your goal is to represent a wire with christmas lights on it. You should be able
to call add_to_chain to add a light to the end of the wire.
You should also be able to print out the list of wires.