Sink drain configuration

In this picture of a bathroom sink drain from a four year old condo, a braided steel supply line connects a cast metal drain pipe to what seems to be a supply in the wall. This flexible line is independent of the hot and cold supplies that feed the faucet valves. Anyone familiar with this configuration? I’ve never seen it before.

-Jim Gallant


Is it a HVAC condensate drain line?

I’ll bet that’s it now that you mention it.