public function inherit($outline = null)
    {
        $this->init();
 
        $list = [];
        foreach ($this->inherit as $name => $item) {
            if (isset($item->inherit->particle)) {
                $list[$item->inherit->outline][$name] = $item->inherit->particle;
            } else {
                $list[$item->inherit->outline][$name] = $name;
            }
        }
 
        return $outline ? (!empty($list[$outline]) ? $list[$outline] : []) : $list;
    }
 
    /**
     * Return atoms from the layout.
     *
     * @return array|null