src/Entity/AddressValidationResponse.php
public function isValid()
    {
        if (AddressValidation::REQUEST_OPTION_ADDRESS_CLASSIFICATION == $this->requestAction) {
            return $this->response->AddressClassification->Code > 0;
        }
        return isset($this->response->ValidAddressIndicator);
    }
public function isValid()
    {
        if (AddressValidation::REQUEST_OPTION_ADDRESS_CLASSIFICATION == $this->requestAction) {
            return $this->response->AddressClassification->Code > 0;
        }
        return isset($this->response->ValidAddressIndicator);
    }
Tells whether or not the ValidAddressIndicator is present on the XML document.
This indicator is present if provided address is valid and represents a
single, unique address in the UPS Address Validation system.

@return bool