code: @Override
    public void terminate(final TestSession session, final SessionTerminationReason reason) {
      // Thread safety reviewed
      new Thread(() -> _release(session.getSlot(), reason)).start();
    }
docs: Ends this test session for the hub, releasing the resources in the hub / registry. It does not
  release anything on the remote. The resources are released in a separate thread, so the call
  returns immediately. It allows release with long duration not to block the test while the hub is
  releasing the resource.
  
  @param session The session to terminate
  @param reason  the reason for termination