Represent File Uploads in API Blueprints

Question

We have an API end point where an image file can be uploaded along with the name of the file (a string) as well as a description (string).

Apiary / API Blueprints won't allow me to have something like:

+ Request (multipart/form-data)

  + Headers

              Authorization: [key]

  + Attributes
      + name (string, required) - A human-readable name of the Catalog Item
      + description (string, optional) - A human readable description of the Catalog Item
      + image (file, optional) - An image file corresponding to the Catalog Item

I get:

base type 'file' is not defined in the document

Is there a way to represent multipart/form-data such as the above in API Blueprints?

Stridulate