cumulative_logprob is None

[ChicyChen]

Hi authors,

When I try to run the vLLM demo, it turns out cumulative_logprob is None in the below line:
watermark_ppl = np.mean([-output.outputs[0].cumulative_logprob/len(output.outputs[0].token_ids) for output in outputs])
Do you have any suggestions on why this is happening?

Thanks

[srao-cipher]

Happening for me too, did you figure it out?