code: def register_handler(alias: str, handler: callable):
          
          if SignalDispatcher.handlers.get(alias) is None:
              SignalDispatcher.handlers[alias] = [handler]
          else:
              SignalDispatcher.handlers.get(alias).append(handler)
docs: Used to register handler at the dispatcher.
  
          :param alias: Signal alias to match handler to.
          :param handler: Handler. Some callable.
          :return: