Paperclip CLI fails on openapi v3: YAML error: missing field `swagger`

I built paperclip master CLI with

> cargo install --path . --features cli,v3,codegen,chrono,url,uuid

(Did I miss a feature needed?)

When I use it with a v3 spec, I get

> paperclip --out models_paperclip my_spec.yaml --api v3
YAML error: missing field `swagger` 

If I convert the same spec to v2, using https://github.com/LucyBot-Inc/api-spec-converter, it works perfectly

> api-spec-converter my_spec.yaml --from=openapi_3 --to=swagger_2 > my_spec_v2.yaml
> paperclip --out models_paperclip my_spec_v2.yaml --api v2