This is an Educational Testing Service XML format based on the QTI specification.
As you can see below, this XML spec nests <item> tags that essentially mean different
things. In this case, the first <item> tag level below organization is what I would
term "subject", the second level is what I would term "grade", and the third level is
the thing I actually reference as an "item". I need to capture the subject and grade
information, but when I process "items", I only want those ones at the third level.

Ideally, I'd like to be able to reference:

manifest.subject //Math
manifest.subject.grades
manifest.subject.grades[n].items

But I can't figure out how to write the class definitions for HappyMapper use,
because everything's an <item>. The different <item> tags have attributes that
appear to reliably identify the pieces, but not sure how to use that to my
advantage.