Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Calculation/Functions.php
public static function isBlank($value = null)
    {
        if ($value !== null) {
            $value = self::flattenSingleValue($value);
        }

        return $value === null;
    }
public static function isBlank($value = null)
    {
        if ($value !== null) {
            $value = self::flattenSingleValue($value);
        }

        return $value === null;
    }
IS_BLANK.

@param mixed $value Value to check

@return bool