lib/AdobeMarketingCloud/OptionParser.php
public function isOptional($flag)
    {
        $rule = $this->getRule($flag);
        return $rule && $rule['required'] === self::PARAM_OPTIONAL;
    }
public function isOptional($flag)
    {
        $rule = $this->getRule($flag);
        return $rule && $rule['required'] === self::PARAM_OPTIONAL;
    }
Returns true if the given flag is optional.

@return  bool