As the C implementation is already shadowing the Python implementation when available (last lines of Lib/xml/etree/ElementTree.py), using `.copy()` is already a bug magnet (works when the Python implem is used, does not work when shadowed by the C implem).

So renaming the copy method to __copy__ in the python implementation looks good to me.

Ultimately the Python implementation would require a __deepcopy__ too?