Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Reader/Xls/Style/FillPattern.php
public static function lookup($index)
    {
        if (isset(self::$map[$index])) {
            return self::$map[$index];
        }

        return Fill::FILL_NONE;
    }
public static function lookup($index)
    {
        if (isset(self::$map[$index])) {
            return self::$map[$index];
        }

        return Fill::FILL_NONE;
    }
Get fill pattern from index
OpenOffice documentation: 2.5.12.

@param int $index

@return string