@Override
    public int hashCode() {
        int result = applicationHostRole.hashCode();
        result = 31 * result + applicationContainerRole.hashCode();
        return result;
    }
@return an ApplicationRoles instance if both hostRole and containerRole is non-empty, <code>null</code> otherwise
config-model-api/src/main/java/com/yahoo/config/model/api/ApplicationRoles.java