getFile from rest api and swagger

I use a swagger file and ##class(%REST.API).CreateApplication to create the rest api.

There is an interesting post: https://community.intersystems.com/post/download-file-rest-api-operation, but it is code, not a swagger configuration. disp.cls returns always a header content : application/json that of course fails as I am not always returning a json

I can not figure out what to put in swagger. Some examples I tried:

produces:
- application/pdf
- image/png

responses:
   200:
      schema:
           type: file
responses:
   200:
       schema:
           type: string
           format: binary

Thank you