Bolt\Storage\Field\Type\ListTypeBase::persist PHP Method

    public function persist(QuerySet $queries, $entity)
    {
        $key = $this->mapping['fieldname'];
        $value = $entity->get($key);
        if ($value !== null && !empty($value)) {
            $value = $this->isJson($value) ? json_decode($value, true) : $value;
            // Remove elements that are not important for storage.
            foreach ($value as &$v) {
                unset($v['id']);
                unset($v['order']);
                unset($v['progress']);
                unset($v['element']);
            }
        }
        $entity->set($key, $value);
        parent::persist($queries, $entity);
    }