title: knockout.js accessing container model property in a contained viewModel
body: <p>I have nested view models like below.  I am trying to access value in container view model from the contained view model (child).  I got undefined error when the modelA.prop1 trying to get mainVM.prop1 value.  Thanks for your help.</p>
  
  <pre><code>function mainVM() {
  
      var self = this;
  
      //chain associated view models
      self.modelA = new modelA();
      self.modelB = new modelB();
  
      self.prop1 = ko.observable("some value from mainVM.prop1");
  
  }
  function modelA(){
     var self = this;
     self.prop1 = ko.observable(mainVM.prop1); //I'd like to get value in containing view model above
  }
  function modelB(){....}
  
  $(function () {
      var viewModel = new mainVM();
      ko.applyBindings(viewModel);
  });
  </code></pre>