unregister method
Unregister a registered service
Pass the unique id
of the Service.
If a service is already loaded it can't be unregistered.
Implementation
void unregister(String id) {
if (!has(id)) {
throw ServiceNotFoundException('The service "$id" does not exist');
} else if (_loadedServices.containsKey(id)) {
var msg =
'The service "$id" can not be unregistered because it\'s loaded';
throw Exception(msg);
}
_services.remove(id);
}