sclass FlexThreadLocal<A> extends BetterThreadLocal<A> {
  static Map<Thread> motherThreads = weakMap();

  public A get() {
    ret get(grandMotherThread());
  }
  
  void set(A a) {
    map.put(grandMotherThread(), a);
  }
  
  static Thread grandMotherThread(Thread t default currentThread()) {
    ret applyWhileNotNull motherThread(t);
  }
  
  static void setMotherThread(Thread t) {
    mapPutOrRemove(motherThreads, currentThread(), grandMotherThread(t));
  }
  
  static Thread motherThread(Thread t default currentThread()) {
    ret mapGet(motherThreads, t);
  }
}