@Override
    public String getId() {
        return StringUtils.defaultIfBlank(super.getId(), DuoSecurityMultifactorAuthenticationProperties.DEFAULT_IDENTIFIER);
    }
This is {@link DefaultDuoSecurityMultifactorAuthenticationProvider}.

@author Misagh Moayyed
@since 5.0.0
support/cas-server-support-duo-core-mfa/src/main/java/org/apereo/cas/adaptors/duo/authn/DefaultDuoSecurityMultifactorAuthenticationProvider.java