pocketmine\event\TranslationContainer::setParameter PHP Method

    public function setParameter($i, $str)
    {
        if ($i < 0 or $i > count($this->params)) {
            //Intended, allow to set the last
            throw new \InvalidArgumentException("Invalid index {$i}, have " . count($this->params));
        }
        $this->params[(int) $i] = $str;
    }