private function createInsertObj(Model $model)
    {
        $metadata = $model->getMetadata();
        $insert = [
            $this->getIdentifierKey()   => $this->convertId($model->getId()),
        ];
        if (true === $metadata->isChildEntity()) {
            $insert[$this->getPolymorphicKey()] = $metadata->type;
        }
        return $this->appendChangeSet($model, $insert, $this->getCreateChangeSetHandler());
    }