MasterCylinder Wiring

OK, I know this is just plain stupid. But how the heck do I release and unplug the wiring connector on the MC reservoir of my '95 Olds 88 Royale?

I've pushed, pulled and everything else I can think of on the piece that appears to be the release. Short of over forcing it, I am stumped. No, I don't have other GM cars, so I am not acquainted with this gizmo.

I plan to remove the MC and take it with me to get the new one, so I don't have the new one to look at.

Thanks