* {@code acquiredLock}, or in the {@code disallowedPriorLocks} map, in which case it is not
     * safe.
     */
    void checkAcquiredLock(Policy policy, LockGraphNode acquiredLock) {
      // checkAcquiredLock() should never be invoked by a lock that has already
      // been acquired. For unordered locks, aboutToAcquire() ensures this by