code: private void aboutToAcquire(CycleDetectingLock lock) {
      if (!lock.isAcquiredByCurrentThread()) {
        ArrayList<LockGraphNode> acquiredLockList = acquiredLocks.get();
        LockGraphNode node = lock.getLockGraphNode();
        node.checkAcquiredLocks(policy, acquiredLockList);
        acquiredLockList.add(node);
      }
    }
docs: CycleDetectingLock implementations must call this method before attempting to acquire the lock.