private void unblockNamespace(final UnblockNamespace command) { final String namespace = command.getNamespace(); final ActorRef sender = getSender(); final ActorRef self = getSelf(); blockedNamespaces.remove(namespace) .thenAccept(_void -> { final UnblockNamespaceResponse response = UnblockNamespaceResponse.getInstance(namespace, command.getResourceType(), command.getDittoHeaders()); sender.tell(response, self); }) .exceptionally(error -> handleError(error, command, sender)); }