code: public <T> void register(String subjectName,
                                     SubjectObserver<T> subjectObserver,
                                     Subject<T> subject)
     {
        subject.add(subjectObserver);
        
        this.registry.put(subjectName, subject);
     }
docs: Add subject observer to a subject
  @param <T> the class type
  @param subjectName the subject name
  @param subjectObserver the subject observer
  @param subject the subject to add the observer