bug: [serve] `serve-grpc` failed: <class '_bentoml_sdk.service.factory.Service'> type doesn't support gRPC serving

[zxpshadow-prog]

Describe the bug

bentoml 1.4.39

1.run http, it is ok.
bentoml serve ./xinfra/supervisor/service.py:Supervisor --port 9099
output:
2026-05-11T09:25:47+0800 [INFO] [cli] Starting production HTTP BentoServer from "./xinfra/supervisor/service.py:Supervisor" listening on http://localhost:9099 (Press CTRL+C to quit)
2026-05-11T09:25:48+0800 [INFO] [entry_service:Supervisor:1] Service Supervisor initialized
2026-05-11T09:26:08+0800 [INFO] [entry_service:Supervisor:1] 127.0.0.1:61898 (scheme=http,method=GET,path=/,type=,length=) (status=200,type=text/html; charset=utf-8,length=2945) 330.566ms (trace=53e4c15be8bbe08a7c76051676e5a9ab,span=2a5d06d5d1994513,sampled=0,service.name=Supervisor)

2.run grpc fail
bentoml serve-grpc ./xinfra/supervisor/service.py:Supervisor --port 9098
Error: [serve] serve-grpc failed: <class '_bentoml_sdk.service.factory.Service'> type doesn't support gRPC serving

Could you help me with running gRPC? Thank you very much！

To reproduce

No response

Expected behavior

No response

Environment

bentoml 1.4.39
python 3.12
win11 uv