How does protocomm-nimble write to GATT characteristic?

[karunt]

I'm using the wifi provisioning example, which seems to use the protocomm-nimble protocol to read data sent to the chip via bluetooth. But how does protocomm-nimble write to a GATT characteristic after a certain event occurs? I can't figure out which function is used by protocomm-nimble to do that. Any help is appreciated.