oj-combobox with RESTDataProvider: options are displayed mulitiple times

Hello everybody!

I try to use the new RESTDataProvider to feed the options of oj-combobox.

The desired output are seven keywords, but what happens is that the options (keywords) are displayed multiple times.

I have no idea how to control this behaviour. Is there anyone who has an idea what´s going wrong?

** HTML **

<oj-combobox-many id="keywordsDropDown"

      value-options="{{selectedKeywords}}"

      options="[[keywordRestDataProvider]]"

      options-keys.value="id"

      options-keys.label="text">                     

 </oj-combobox-many>

**Typescript**

   const optionsKeywordsDataProvider = {   

url: self.keywordsURL,

     keyAttributes: "id",

     transforms: {

       fetchFirst: {

         request: async (options) => {

           const url = new URL(options.url);

           return new Request(url.href);    },

         response: async ({ body }) => {

           const keywords = self.parseKeywordsResponseBody(body);

           return { data : keywords };

         } } } };

   self.keywordRestDataProvider = new RESTDataProvider(optionsKeywordsDataProvider);

parseKeywordsResponseBody = (body) => {

   var result = [];

   if ((body._embedded != null) && (body._embedded.keywords != null)) {

     result = body._embedded.keywords;    }

   return result;  };