public function generateDeletedProxies()
    {
        $droppedProxies = array_diff($this->oldProxyKeys, $this->newProxyKeys);

        foreach ($droppedProxies as $droppedProxy) {
            $modelState = $this->fromState->getModelState($droppedProxy);
            $meta = $this->oldRegistry->getModel($droppedProxy)
                ->getMeta();

            // create operation
            $this->addOperation(
                $meta->getAppName(),
                DeleteModel::createObject(
                    [
                        'name' => $modelState->name,
                    ]
                )
            );
        }
    }