In knockout.js 2.1.0, in a template using the foreach binding, you can access the current item's index though the $index() function. In a nested foreach binding, is there any way to access the index of the $parent from a template?

Say I have a data structure like this:

var application = {

  topModel: [

    {

      {subModel: [{'foo':'foo'}, { 'bar':'bar'}]}, // this has top:0 and sub:0

      {subModel: [{'foo2':'foo2'}, { 'bar2':'bar2'}]} // this has top:0 and sub:1

    },

    {

      {subModel: [{'foo':'foo'}, { 'bar':'bar'}]} // this is top:1 sub:0

    },

    {

      {subModel: [{'foo':'foo'}, { 'bar':'bar'}]} // this is top:2 sub:0

      {subModel: [{'foo':'foo'}, { 'bar':'bar'}]} // this is top:2 sub:1

    },

    ...

    ]};

With this, I want to print the path to each model, using indices:
[topModel-index subModel-index], so that the output will be something like:

[0 0]

[0 1]

[1 0]

[2 0]

[2 1]

...

I have bound the models using foreach, but I can't figure out how to access the topModel's index in the context of the subModel. The following example shows an approach I have tried, but it doesn't work, as I can't figure out how to access the index of the $parent referrer.

<!--ko foreach: topModel -->

<!--ko foreach: subModel -->

  [<span data-bind=text: $parent.index()></span>

  <span data-bind=text: $index()></span>]

<!--/ko-->

<!--/ko-->

Should print out: 0 1, 0 2, 1 0, 1 1, 1 2, 2 0, 2 1, ...