[IronPython] Referring to Python types in Xaml

[Bish Bosh]

What is the mechanism for making types in the Python domain available
to the WPF type system for use in a Xaml file?

In the code below I am refering to the Python class to do some
formatting but would have the same problem if I was trying to create
an instance of a Python class in the Xaml file.  Any ideas? I'm pretty
sure I'm missing something simple but fundamental.  As usual.

In Python file I have a type:

  class FancyData(ObservableCollection[str]):
    pass

The collection to be displayed I am adding as an application resource:

   app.Resources.Add('collection', FancyData())

So it can be bound to as expected in the Xaml:

  <ListBox ItemsSource="{Binding Source={StaticResource collection}}"/>

In Xaml file I would like to refer to the type to do some formatting:

  <DataTemplate DataType="{x:Type FancyData}">
    <StackPanel>
       ...

I get the error:

  File data1.py, line 108, in Initialize
  File , line 0, in _stub_##77
  File data1.py, line 26, in LoadXaml
  File , line 0, in _stub_##87
  File PresentationFramework, line unknown, in Load
  File PresentationFramework, line unknown, in XmlTreeBuildDefault
  File PresentationFramework, line unknown, in Parse
  File PresentationFramework, line unknown, in ParseFragment
  File PresentationFramework, line unknown, in _Parse
  File PresentationFramework, line unknown, in ReadXaml
  File PresentationFramework, line unknown, in Read
SystemError: Type reference cannot find public type named 'FancyData'.