How Come Pythonista's Notification Module Won't Honor My Sound Choice?

Question

I'm using Pythonista 3, and the built in notification module. When I run the script, and sleep the device, it uses the default sound instead of the one I passed in to the schedule function. For the sake of argument (with myself, of course. Who doesn't argue with themselves from time to time?) I tried passing in different sounds from different files, with the same result: the default iOS sound is played. I'm using iOS 9.3.4 on an iPod touch 6th gen (their newest).

Here's my code, if you want to see it:

import notification
import sound

notification.schedule("Hello World!",5,'digital:PhaserUp7','http://apple.com')

sound.play_effect('digital:PhaserUp7')

The only other thing I can think of is that I used their newish "media adder" feature at the top left corner to get the sound file names.

Thank you!