code: private void addSuperClasses(Integer directSuperClass,
  			ClassRecord subClassRecord) {
  		if (subClassRecord.superClasses.contains(directSuperClass)) {
  			return;
  		}
  		subClassRecord.superClasses.add(directSuperClass);
  		ClassRecord superClassRecord = getClassRecord(directSuperClass);
  		if (superClassRecord == null) {
  			return;
  		}
  
  		for (Integer superClass : superClassRecord.directSuperClasses) {
  			addSuperClasses(superClass, subClassRecord);
  		}
  	}
docs: Recursively add indirect subclasses to a class record.
  
  @param directSuperClass
  the superclass to add (together with its own superclasses)
  @param subClassRecord
  the subclass to add to