* function in the Actor::on_termination signal, that is shared between
* all actors. Callbacks to this signal are executed for each terminating
* actors, no matter what. This is useful in many cases, in particular
* function in the Actor::on_termination signal, that is shared between
* all actors. Callbacks to this signal are executed for each terminating
* actors, no matter what. This is useful in many cases, in particular