code: @Override
    public FailsafeExecutor<R> onSuccess(CheckedConsumer<? extends ExecutionCompletedEvent<R>> listener) {
      return super.onSuccess(listener);
    }
docs: Registers the {@code listener} to be called when an execution is successful. If multiple policies, are configured,
  this handler is called when execution is complete and <i>all</i> policies succeed. If <i>all</i> policies do not
  succeed, then the {@link #onFailure(CheckedConsumer)} registered listener is called instead.