[IronPython] Where is Application.LoadRootVisual() documented?

[Andy Sy]

Silverlight Iron Python examples show the following method
to load an external XAML file:

   Application.Current.LoadRootVisual(ControlName(),"blah.xaml")

Trouble is, I don't see LoadRootVisual() referred to in the
Silverlight API reference.  Is this IronPython specific and
if so, is there a reference document that lists all such
functions?