* call to `new SupplantableFuture` below.)
       */
      @SuppressWarnings("GuardedBy")
      private Cancellable initializeOrUpdateCancellationDelegate(Schedule schedule) {
        if (cancellationDelegate == null) {
          return cancellationDelegate = new SupplantableFuture(lock, submitToExecutor(schedule));
        }

       * call to `new SupplantableFuture` below.)
       */
      @SuppressWarnings("GuardedBy")
      private Cancellable initializeOrUpdateCancellationDelegate(Schedule schedule) {
        if (cancellationDelegate == null) {
          return cancellationDelegate = new SupplantableFuture(lock, submitToExecutor(schedule));
        }