code: public Set<Class<?>> getConcreteClasses() {
          Set<Class<?>> concreteClassSet = new LinkedHashSet<>();
  
          for ( Class<?> clazz : classes ) {
              if ( isConcrete(clazz) ) {
                  concreteClassSet.add(clazz);
              }
          }
  
          return concreteClassSet;
      }
docs: Fetches the set of classes discovered so far, subsetted down to concrete (non-abstract/interface) classes only
  
  @return subset of classes discovered so far including only concrete (non-abstract/interface) classes