code: def vrrp_list(app, instance_name=None):
      
      list_request = vrrp_event.EventVRRPListRequest(instance_name)
      list_request.dst = vrrp_event.VRRP_MANAGER_NAME
      return app.send_request(list_request)
docs: list instances.
      returns EventVRRPListReply([VRRPInstance]).