docs: public static void load(Class<?> restrictionClass) {
      if(MASTER_CACHE == null) {
        initialize();
      }
      if(MASTER_CACHE.isEmpty()) {
        return;
      }
      Iterator<Class<?>> iter = MASTER_CACHE.iterator();
      while(iter.hasNext()) {
        Class<?> clazz = iter.next();
        // Skip other classes.
        if(!restrictionClass.isAssignableFrom(clazz)) {
          continue;
        }
        // skip abstract / private classes.
        if(Modifier.isInterface(clazz.getModifiers()) || Modifier.isAbstract(clazz.getModifiers()) || Modifier.isPrivate(clazz.getModifiers())) {
          continue;
        }
        boolean instantiable = false;
        try {
          instantiable = clazz.getConstructor() != null;
        }
        catch(Exception | Error e) {
          // ignore
        }
        try {
          instantiable = instantiable || ClassGenericsUtil.getParameterizer(clazz) != null;
        }
        catch(Exception | Error e) {
          // ignore
        }
        if(!instantiable) {
          continue;
        }
        ELKIServiceRegistry.register(restrictionClass, clazz);
      }
    }