Custom Configuration Section - Multiple Collections

Question

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How to Create a Configuration Section That Contains a Collection of Collections?

I would like to create something like this custom section in a web.config

<MyCustomSection>
     <Collection name="test">
        <item name="foo" />
        <item name="bar">
     </Collection>
     <Collection name="test2">
        <item name="bob" />
        <item name="joe" />
     </Collection>
     ...
</MyCustomSection>

I've seen a number of tutorials show how to create a Collection (like this one: http://dotnetslackers.com/articles/customconfiguration/Custom_Configuration_Collections.aspx) but nothing showing how to create a collection of collections. Is this even possible?