Fetch API type Relation – SWAPI The Star Wars API (JavaScript)

I’m having a hard type to fetch the itens on this many-to-many relation between Characters and Films, I get an Array, but it’s empty.

const relation_where_films = encodeURIComponent(JSON.stringify({
            "characters":{
              "__type": "Relation",
              "className": "SWAPI_Character",
              "objectId": get_data,
            }
        }));
          (async () => {
            const resp_films = await fetch(
              `https://parseapi.back4app.com/classes/SWAPI_Film?&where=${relation_where_films}`,
              {
                headers: {
                  'X-Parse-Application-Id': 'API-ID',
                  'X-Parse-REST-API-Key': 'API-KEY',
                }
              }
            );
            const films = await resp_films.json();

            var obj_films = films.results;
  
            console.log(obj_films);

          })();

I would really appreciate if somenone tell me what what is wrong, even a tip would come in handy.