code: public Query setFacetFilters(List<String> facets) {
      JSONArray obj = new JSONArray();
      for (String facet : facets) {
        obj.put(facet);
      }
      this.facetFilters = obj.toString();
      return this;
    }
docs: Filter the query by a list of facets. Each filter is encoded as
  `attributeName:value`.