Library does not hadle option regex group

[luiscoms]

Describe the bug
My api have an optional group on route, and it braaks on start when I use tornado-swagger library

To Reproduce
Steps to reproduce the behavior:

My api is configured as above

    handlers = [
        url(r'/(?:status)?', StatusHandler),
        # other handlers
    ]
    setup_swagger(handlers)

    app = Application(handlers)

When I run, the following error occurs:

File "/project/path/venv/lib/python3.8/site-packages/tornado_swagger/setup.py", line 58, in setup_swagger
    swagger_schema = generate_doc_from_endpoints(
  File "/project/path/venv/lib/python3.8/site-packages/tornado_swagger/_builders.py", line 276, in generate_doc_from_endpoints
    return doc_builders[api_definition_version].generate_doc(
  File "/project/path/venv/lib/python3.8/site-packages/tornado_swagger/_builders.py", line 240, in generate_doc
    "paths": _extract_paths(routes),
  File "/project/path/venv/lib/python3.8/site-packages/tornado_swagger/_builders.py", line 124, in _extract_paths
    paths[_format_handler_path(route, method_name)].update({method_name: method_description})
  File "/project/path/venv/lib/python3.8/site-packages/tornado_swagger/_builders.py", line 94, in _format_handler_path
    route_pattern = route_pattern.replace(entity, "{%s}" % parameters[i], 1)
IndexError: list index out of range

It is because there is no parameter

Expected behavior

The aplications should show urls like this

Additional context

For now, I am duplicating entry, but It sims not correct for me

    handlers = [
        url(r'/', StatusHandler),
        url(r'/status', StatusHandler),
        # other handlers
    ]
    setup_swagger(handlers)

    app = Application(handlers)

[mrk-andreev]

Issue with IndexError was fixed in 1.4.4. Actual behavior is ignore paths like this.

I think that use optionals in path does not cover rest api url convention best practices. Unfortunately I have no plant for support every regexp in path. Furthermore tornado does not recognize this regexp, too.