docs: function setupNotifier (scope, notifierMap) {
      function handler (notifierKey, newValue, oldValue) {
        if (newValue !== oldValue) {
          scope.$broadcast('$$rebind::' + notifierKey);
        }
      }
  
      Object.keys(notifierMap).forEach(function (k) {
        scope.$watch(
          notifierMap[k],
          handler.bind(null, k),
          typeof scope[notifierMap[k]] === 'object'
        );
      });
    }