How do I use environmental variables in yaml

Question

In my yaml file for my nextjs project using netlify-cns

I have a config.yaml file.

and I need to access the process.env.APIKEY

here is my code

media_library:
  name: cloudinary
  config:
    cloud_name: ponders-east
    api_key:  ${process.env.CLOUDINARY_API}

how do I transform this into the appropriate yaml file?