private function addItem()
    {
        $args = func_get_args();
        if (in_array($args[0], self::$appendableTransformations)) {
            $i = $this->findLastTransformation($args[0]);
            if ($i !== false) {
                $this->items[$i]['rendered'] .= ','.implode(':', array_slice($args, 1));

                return $this;
            }
        }
        if ($args[0] != '/' && $this->itemCount && in_array($this->items[$this->itemCount - 1]['type'], self::$forcedLastTransformations)) {
            $lastTransformation = array_pop($this->items);
        }
        $this->items[] = [
            'type' => $args[0],
            'rendered' => implode(':', $args),
        ];
        ++$this->itemCount;
        if (isset($lastTransformation)) {
            $this->items[] = $lastTransformation;
        }

        return $this;
    }