Coding:
CI/CD: 
/** Heya this is Yen, I code backend for problem solving */
import io.reactivex.rxjava3.core.Observable;
public class MyStack {
interface Skill {}
static class BackendDevelopment implements Skill {
String name;
BackendDevelopment(String name) { this.name = name; }
}
static class DataEngineering implements Skill {
String name;
DataEngineering(String name) { this.name = name; }
}
static class SystemArchitecture implements Skill {
String name;
SystemArchitecture(String name) { this.name = name; }
}
public static Observable<String> run(Skill skill) {
return Observable.create(emitter -> {
if (skill instanceof BackendDevelopment) {
emitter.onNext("build backend services with JVM, Python");
} else if (skill instanceof DataEngineering) {
emitter.onNext("big data, streaming, data platform development");
} else if (skill instanceof SystemArchitecture) {
emitter.onNext("system design, product ownership");
} else {
emitter.onNext("other awesome works");
}
emitter.onComplete();
});
}