Xpressengine\Document\Models\Document::setReply PHP Method

    public function setReply()
    {
        $timestamp = time();
        if ($this->parentId == null || $this->parentId == '') {
            $this->setAttribute('head', $timestamp . '-' . $this->id);
        } elseif ($this->parentId !== $this->id) {
            $parent = static::find($this->parentId);
            if ($parent === null) {
                throw new ParentDocumentNotFoundException();
            }
            $this->setAttribute('reply', $this->getReplyChar($parent));
            $this->setAttribute('head', $parent->head);
        }
        $this->setAttribute('listOrder', $this->head . (isset($this->reply) ? $this->reply : ''));
    }