call the method handler.addQuickElement with 3 arguments: string 'link', an empty string and a dictionary with 4 entries:
handler . addQuickElement ( "link" , '' , { "rel" : "enclosure" , "href" : item [ 'enclosure' ] . url , "length" : item [ 'enclosure' ] . length , "type" : item [ 'enclosure' ] . mime_type } )