The cylinder is having electric/electronic plug in it, very likely a sensor.
My crystal ball would put charcoal tank venting as first suspect, but why not go with the picture to a dealer and ask?
You can make up a story that you think you have something missing out there and friendly dealer will provide you with blown-up drawing showing whole assemble.
I have mechanical education and have been auto-hobbyist my whole life, but when I pick up new truck, I open the hood, spend about 2 minutes trying to figure out what is what and close it with no intention to go farther with my investigation till the warranty will expire.