@Override
    public Set<String> getAttributeRepositoryIds() {
        return repositories.stream()
            .map(RegisteredServicePrincipalAttributesRepository::getAttributeRepositoryIds)
            .filter(Objects::nonNull)
            .flatMap(Set::stream)
            .collect(Collectors.toSet());
    }
This is {@link ChainingPrincipalAttributesRepository}.

@author Misagh Moayyed
@since 6.5.0
core/cas-server-core-authentication-attributes/src/main/java/org/apereo/cas/authentication/principal/ChainingPrincipalAttributesRepository.java