It would be good, I think, to assert something about the results of the export.

In particular, I think the thing that concerned me about the fix in the raw module is whether it would cause issues for other subclasses of `RawDescriptor` that didn't expect `self.data` to be empty, and whether an an export/import pair would leave `self.data` in the same state.

To be even more specific: If I `del foo.data`, and then export, and then re-import, won't `foo.data == '<foomodule/>'`, and `foo.data != None`. That seems like it could cause problems.