code: @Override
      public ResolverHook begin(Collection<BundleRevision> triggers) {
          ResolverHook hook = null;
          // Only return hook if resolve is on behalf of the thread that started this handler;
          if (_resolvingThread == Thread.currentThread().getId()) {
              hook = this;
          }
          return hook;
      }
docs: ** overrides from ResolverHookFactory ****