As an FYI, nosferatu-man's and my solutions are better than S. Carton's, but require Python 2.4. The "key" parameter to sort/sorted does a "Decorate-Sort-Undecorate"[1] automatically, whereas the ...

Alternatively, the cast / validate method should not check for the validity of the nested arrays, when the parent struct array isn't valid/is null for this element. Though I don't think this is a good ...