code: function syncItems(system, front, customProps) {
    return front.specs(customProps).then(function(specs) {
      removeItemsFromFront(system, front);
  
      var remoteItems = addLocalFunctions(specs, front);
      system.addItems(remoteItems);
  
      return system;
    });
  }
docs: Remove the items in this system that came from a previous sync action, and
  re-add them. See connectFront() for explanation of properties