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* Rename type variable ``EXPLICIT_NULL`` to ``ExplicitNull``
* Rename module ``type_defs.py`` to ``type_def.py``
* Rename module ``base_meta.py`` to ``bases_meta.py``
* ``JSONSerializable.Meta``: rename attribute ``date_time_with_dump`` to ``marshal_date_time_as``, as I believe
this name is overall more clearer.
* Refactor the ``property_wizard`` helper function and update it to cover some edges cases.
* Add test cases to confirm intended functionality of ``property_wizard``.