container start fail with sanic+sanic-openapi

I have a simple sanic server, it runs ok with normal docker, but failed to launch when slimed.

$ docker build -t server .
$ docker-slim build server .
$ docker run -d server.slim

and container exit with error

Traceback (most recent call last):
  File "main.py", line 12, in <module>
    app.blueprint(swagger_blueprint)
  File "/usr/local/lib/python3.7/site-packages/sanic/app.py", line 726, in blueprint
    blueprint.register(self, options)
  File "/usr/local/lib/python3.7/site-packages/sanic/blueprints.py", line 158, in register
    uri, future.file_or_directory, *future.args, **future.kwargs
  File "/usr/local/lib/python3.7/site-packages/sanic/app.py", line 704, in static
    content_type,
  File "/usr/local/lib/python3.7/site-packages/sanic/static.py", line 146, in register
    )(_handler)
  File "/usr/local/lib/python3.7/site-packages/sanic/app.py", line 201, in response
    name=name,
  File "/usr/local/lib/python3.7/site-packages/sanic/router.py", line 147, in add
    self._add(uri, methods, handler, host, name)
  File "/usr/local/lib/python3.7/site-packages/sanic/router.py", line 303, in _add
    route = merge_route(route, methods, handler)
  File "/usr/local/lib/python3.7/site-packages/sanic/router.py", line 255, in merge_route
    uri, ",".join(list(duplicated))
sanic.router.RouteExists: Route already registered: /swagger/<file_uri:/?.+> [HEAD,GET]

code as below, include main.py, Dockerfile and requirements.txt

Dockerfile

FROM python:3.7
COPY requirements.txt /requirements.txt
RUN pip install -r requirements.txt

COPY . /app
WORKDIR /app
EXPOSE 8000
CMD python main.py

main.py

from sanic import Sanic
from sanic_openapi import swagger_blueprint
app = Sanic()
app.blueprint(swagger_blueprint)
if __name__ == "__main__":
    app.run(host="0.0.0.0", port=8000)

requirements.txt

sanic
sanic-openapi

Note that if I commented out line app.blueprint(swagger_blueprint), slim container can launch success

Reproduce the failure using Dockerfile, main.py, and requirements.txt with the shown docker-slim build and docker run commands. Start by comparing the normal and slimmed containers around app.blueprint(swagger_blueprint); done means the slimmed container launches successfully without removing that blueprint.