Sadly Apple now uses a very different removable SSD from the older retina models. Here's an image of the older model custom SSD:

Here is the late 2016 function key model's custom SSD and I suspect they are still using it in the 2017 series:

Here's the IFIXIT teardown where you can see the full story: MacBook Pro 13" Function Keys Late 2016 Teardown

At least this model has a removable SSD! The Touch Bar models use soldered SSD chips directly on the logic board and are not upgradable!

Now the rub... It took close to three years before a 3rd party (OWC) was able to make a compatible SSD for the older retina models. So while its replaceable it may not be upgradable by a 3rd party ($$$).