Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Calculation/Functions.php
public static function isErr($value = '')
    {
        $value = self::flattenSingleValue($value);

        return self::isError($value) && (!self::isNa(($value)));
    }
public static function isErr($value = '')
    {
        $value = self::flattenSingleValue($value);

        return self::isError($value) && (!self::isNa(($value)));
    }
IS_ERR.

@param mixed $value Value to check

@return bool