Help identifying this part please?

[latte]

I just got my car fixed for coolant leak, the shop replaced the coolant hose flange and a heater hose. While looking back there just out of curiosity to see what exactly was change I noticed this part that looks like something should be attached to it... But isn't. Can anyone help identify this part for me and confirm whether or not something should be connected to this? It's the part right in the center with the brass threaded nozzle sitting there not attached to anything.

Thanks in advance!

[A4BGP]

Cap No. 06F133335A is supposed to be on there to protect the orifice of that valve.

[B7TitaniumA4]

that's the fuel pressure check valve (like a tire valve stem) it should just have a black rubber cover on it like mentioned above, it does not connect to anything unless your purging pressure or testing with a pressure tester.