So there's this code I've got from a sample by Catherine 
https://github.com/mcclure/analogue-core-template-amaranth/blob/main/src/fpga/core/core_top.v#L498
That… I don't 100% understand but it creates the interface the underlying amaranth code conforms to. 
I'm trying to amend it to work with some third party documentation https://github.com/agg23/analogue-pocket-utils/wiki/Devkit---Debug-Key on my device
I want to interact with one input signal and one output signal that exists in core_top already, as guided by that documentation.
So I add, around line 520 in core_top.v,
```
    .dbg_key_led    ( cart_tran_bank0[5] ),
    .dbg_key_button ( ~cart_tran_bank3[0] ),
```
and add in my amaranth class definition
```
    dbg_key_led     : Out(1)
    dbg_key_button  : In(1)
```
and I immediately get the error
```
Error (13076): The pin "cart_tran_bank0[5]" has multiple drivers due to the constant driver File: C:/Users/Andi/work/f/analogue-core-template-amaranth/src/fpga/apf/apf_top.v Line: 73
```
Am I doing something "obviously" wrong here?

Is "assign" as in the third party documenter's code https://github.com/agg23/analogue-pocket-utils/blob/master/ip/debug_key.v magic?

Does this look like a sign that something's wonky in the basic library code, and I should go to the device's community and ask for help?