TypeError: unsupported operand type(s) for |: 'dict' and 'dict'

My code use to work with fschat==0.2.33 and vllm==0.2.2, but when I migrated to new versions (fschat==0.2.34 and vllm==0.2.6) fastchat is throwing the following error ,

logs from fastchat

`| ERROR | stderr |   File "/usr/local/lib/python3.8/dist-packages/fastchat/serve/vllm_worker.py", line 150, in generate_stream

| ERROR | stderr |     yield (json.dumps(ret | {"finish_reason": None}) + "\0").encode()

| ERROR | stderr | TypeError: unsupported operand type(s) for |: 'dict' and 'dict'

logs from vLLM code

Received request 24bc821beced4a0abf40ac7342134701

Avg prompt throughput: 0.0 tokens/s, Avg generation throughput: 0.0 tokens/s, Running: 1 reqs, Swapped: 0 reqs, Pending: 0 reqs, GPU KV cache usage: 1.9%, CPU KV cache usage: 0.0%

Finished request 24bc821beced4a0abf40ac7342134701.

Start at fastchat/serve/vllm_worker.py line 150 and inspect the generate_stream path that combines ret with the finish-reason field. Reproduce the failure with Python 3.8 and the reported fschat and vllm versions, then verify the behavior with the supported versions. Done means the request completes without this TypeError or the required Python compatibility is clearly identified.