Python command/event registration pattern

I am working on my first service using ddd.

My domain layer looks simillar to:

/ domain
  /A
    /aggregateA.py   -> fires an EventA
    /aggregateARepository.py
  
  /B
    /aggregateB.py
    /aggregateAService.py  <-- Implements an event handler that listens to EventA

So there are multiple event/command handlers in each subfolder.

In the api layer i would like to execute the commands/events.

@router.post("/",..)
async def add_a():
   cmd = CommandA() 
   //execute CommandHandler and EventHandlers for the events that have been raised.

Is there a way to register event/command handlers inside my domain layer other than having:

/domain
  handlers.py
  /a
    ...
  /b
    ...

where handlers.py looks like this (lists all handlers)

command_handlers = { CommandA:  a.command.command_handler_func,
 ...}
event_handlers = { EventA, [ handler1, handler2 , ...]

I tried the following:

handlers.py:

command_handlers = { } # empty, registration happends in each sub module

and then:

domain/a/commandA.py:

from domain.handlers import command_handlers
def command_handler_a(CommandA):
  ....
command_handlers[CommandA] = command_handler_a

and the same for each commands/events in the other subfolders.

This does not seem to work as expected. The command_handlers are empty unless i import domain/a/commandA.py.

To fix this I would have to import all handlers from the subfolders in a signle place, right ? Which defeats the point I'm trying to archieve, decentralized registration.

Is there a best practice for doing this kind of registration ? I am used to frameworks in other languages where all I have to do is annotate the command handler @command_handler, and it magically works.