What do you think if we move the helper function to ListView? 

For example:
```
var ListView = function() {.....
  var observeHelper = {
     observeAndCall: function() { //.... }
  };
};
```
And then we can call the template function in the list view like this:
```
_templateFunc.call(observeHelper, items[i]);
```
In a template, we can create observe a property like this:
```
this.observeAndCall(observable, map);
```