2019 Outback: What is small hose end on left side ?

[Robert11]

Hello,


Have a 2019 Outback.

Was looking under the hood today.
Rarely do.

Anyway, if I stand directly in front, and look to the left side, a bit, I notice what looks
like the termination of a very small hose in a fixture that holds it up vertically.
Close to the front of car.

Also, there seemed to be a small piece of plastic acting, presumably as some
kind of a seal or flapper valve over the end.

What is this please ?

Thanks,
Bob