What does this piece do?

[Kroatsky]

My 1989 Honda CRX HF has this ignition switch with wires bundled together. In pictures attached, it's the black piece with two leads attached, a BLU/WHT and a WHT/BLU. They terminate on the inside to two copper rivets apparently connected to nothing. This black plastic piece is held to the lock cylinder by one screw. What does it do?  

[Kroatsky]

Here's a inside view of the piece in question