nl: "enclosure" for 'rel', field url of value under the "enclosure" key of item dictionary for 'href', field length of value under the "enclosure" key of item dictionary for 'length', and field mime_type of value under the "enclosure" key of item dictionary for 'type'. for every cat in value under 'categories' key of item dictionary,
code: for cat in item [ 'categories' ] :