Medela Symphony Breast Pump - what is this?

[Chococroc]

I'm currently renting a medela symphony breast pump having used one during my hospital stay and got on well with it.
When it arrived I dutifully sterilised it all and put it back together - except I seem to have a piece (hopefully picture attached) left over. Anyone have any idea what it is/where it goes....? I never noticed a piece like this when using the pump before.

I used one during my stay too and have never seen this part before either. Is it working without it?

I haven't used one, but could it be a belt clip, or something to wind the power cable around, or something similarly non-essential?

I have a Symphony too and it doesn't have this part. Assuming the pump works fine without it, I'd not worry and just put it back in the box and return it when you give back the pump. Looks a bit like a valve from another pump that may have got mixed up.

It looks similar to the valve on my Avent hand pump.
My rental Medela lactina has the same valve system as the symphony which is the yellow things with little flexible white discs that press onto the yellow things. Have you got those parts?

Thank you ! Yes, have all the other parts and it's working fine without ( although would love to start getting a bit more out each time!) so I'll just ignore it I think.