Cutsom context pad

In https://github.com/bpmn-io/bpmn-js-examples/tree/master/custom-elements example, we have CustomContextPadProvider.js which adds new icons in contextpad - can someone tell me where do i see this - on click of custom triangle/custom circle - am not getting - “Connect using custom connection” in context pad - as in javascript line number - 34. Am using firefox as browser. Please support.