*/
  private static class LockGraphNode {

    /**
     * The map tracking the locks that are known to be acquired before this lock, each associated
     * with an example stack trace. Locks are weakly keyed to allow proper garbage collection when
     * they are no longer referenced.
     */
    final Map<LockGraphNode, ExampleStackTrace> allowedPriorLocks =
        new MapMaker().weakKeys().makeMap();

    /**