test.ts

      it('remove all attributes and add #aa81', function () {
        var api = util.loadApi(util.data('attr/aa8.raml'));
        var method: hl.IHighLevelNode = <hl.IHighLevelNode>util.xpath(api, "resources[0]/methods[0]");
        var attrs = method.attributes('protocols');
        console.log("Original:\n" + api.lowLevel().unit().contents());
        attrs.forEach(attr => attr.remove());
        console.log("After remove:\n" + api.lowLevel().unit().contents());
        ['HTTP', 'HTTPS', 'HUE'].forEach(val => method.attrOrCreate('protocols').addValue(val));
        console.log("After insert:\n" + api.lowLevel().unit().contents());
        console.log('attributes count: ' + method.attributes('protocols').length); // 4
      });