public function setIndentWidth($indentWidth)
    {
        if (!is_null($indentWidth) &&
            (!is_int($indentWidth) || $indentWidth < 1)
        ) {
            throw new \InvalidArgumentException(
                'indentWidth needs to be null or an integer above 0'
            );
        }

        $this->indentWidth = $indentWidth;

        return $this;
    }