Block: Blinking on/off LEDs in Session View

I've got a simple python script for my Block that I'm pretty happy with but I'd like it to do one more thing that I'm having trouble figuring out. I can make all of the active clip slots (the ones with a clip in them) light up on the Block's LEDs, or I can make them light up when they're playing. However, I'd like them to always be lit and then blink on and off when they are playing, sort of like they do on the Launchpad when a clip is selected. How can I add this to my script?

Thanks