public Optional<String> apiGroup() {
        return Optional.ofNullable(this.apiGroup);
    }
@return APIGroup holds the API group of the referenced subject. Defaults to &#34;&#34; for ServiceAccount subjects. Defaults to &#34;rbac.authorization.k8s.io&#34; for User and Group subjects.
sdk/java/src/main/java/com/pulumi/kubernetes/rbac/v1beta1/outputs/SubjectPatch.java