What is this disk thing in the middle of the fuel line?

[circuit slave]

Hello, I have a 1987 740 Wagon Turbo FI and down near the oil trap
there is a 3/8 plastic "T" with one 3/8 hose going up on top through
the intake near the spring throttle "fishing reel" thingy and over the
fuel rail and injectors. This hose down below has a white and black
plastic disk in between the hose it looks like a "top" you could spin.
It has a 3/8 fitting on either side and is about the size of a quarter.
The only thing on it is marked "ATE" in script and a "3" "and arror to
motor". It looks kind of "fram" brand or "duracraft" like.

It isn't a flame trap, is it? Because it can't be opened. Looks like
a one way valve. You could look through it on one end and it has a
sort of little wheeled screen and the other end is what looks like a
ball. Do I need this? It doesn't look like a Volvo Part.

 

[circuit slave]

Also FYI, the hose that it's inline to is the original Volvo 3/8 hose
stamped with ID and Denmark so I don't think it was put in by a garage.
As a matter of fact the hose looks like it's trumpeted on both sides of
this half white/ black plastic disk, so it may have always been there.

 

[circuit slave]

Found it! It's called the Vacuum Check Valve. Nevermind, hehe!