Compatibilty with Elasticsearch 6.3 about meteor-easy-search HOT 1 OPEN

export const PostsElasticIndex = new Index({
  collection: Posts,
  name: 'postsElasticIndex',
  fields: ['title','content'],
  engine: new ElasticSearchEngine({
    body: function(body, options) {
      delete body.fields;
      delete body.sort;
      body._source= '_id';
      return body;
     } // modify the body that's sent when searching
  }),
  defaultSearchOptions: { limit: 25 }, // default options when searching

})