[Bug]: Should check whether stop sequence appears anyway in the output text instead of just endswith

[yunfeng-scale]

Your current environment

The output of `python collect_env.py`

🐛 Describe the bug

Using mistral-7b-instruct model, and prompt Here is the English alphabet: ABC, temperature 0, stop sequence DE, model would still output DEFGHIJKLMNOPQRSTUVWXYZ... this is because DEF is a token, and stop sequence is only checked with endswith https://github.com/vllm-project/vllm/blob/main/vllm/engine/llm_engine.py#L717 I think instead of we should check string contain.

[njhill]

@yunfeng-scale yes this is definitely a bug, I'm working on a fix.