'How do I parse dynamic keys in retrofit 2 kotlin?

I'm a newbie in using retrofit and I have no idea how to parse the following data in retrofit 2.

the url im using to fetch this response is : link

   "ISBN:9781611748864":{
      "bib_key":"ISBN:9781611748864",
      "info_url":"https://openlibrary.org/books/OL26092341M/The_Complete_Lord_Of_The_Rings_Trilogy",
      "preview":"noview",
      "preview_url":"https://openlibrary.org/books/OL26092341M/The_Complete_Lord_Of_The_Rings_Trilogy",
      "thumbnail_url":"https://covers.openlibrary.org/b/id/7710580-S.jpg",
      "details":{
         "publishers":[
            "Highbridge Company"
         ],
         "classifications":{
            
         },
         "source_records":[
            "amazon:1611748860"
         ],
         "title":"The Complete Lord Of The Rings Trilogy",
         "identifiers":{
            
         },
         "covers":[
            7710580
         ],
         "created":{
            "type":"/type/datetime",
            "value":"2016-10-14T15:00:38.277250"
         },
         "isbn_13":[
            "9781611748864"
         ],
         "last_modified":{
            "type":"/type/datetime",
            "value":"2019-08-11T08:29:49.478037"
         },
         "publish_date":"2012",
         "key":"/books/OL26092341M",
         "latest_revision":4,
         "works":[
            {
               "key":"/works/OL27448W"
            }
         ],
         "type":{
            "key":"/type/edition"
         },
         "revision":4
      }
   }
}

each ISBN number returns a response of a certain book, I can't figure out how to go about with this. Your help is greatly appreciated.



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