[Python-3000] Simplifying pickle for Py3k

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    Georg> I don't envy everyone reading the pickle docs trying to
    Georg> understand which method exactly he has to implement, which is
    Georg> going to be called with what arguments, etc.

Agreed.  I've been going through that (painful) exercise the past couple of
days as I try and figure out what methods my to-be-pickled objects need to
implement.  __reduce__, __reduce_ex__, __getstate__, __setstate__, copy_reg,
__safe_for_unpickling__, __getnewargs__.  Your head starts to swim after
awhile.

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