AssertionError in pickle's memoize function

[Michael Hohn]

Hi,

under python 2.2, the pickle/unpickle sequence incorrectly restores
a larger data structure I have.

Under Python 2.3, these structures now give an explicit exception from 
Pickle.memoize():
    assert id(obj) not in self.memo

I'm shrinking the offending data structure down to find the problem
and provide an easily reproducible example, 
but maybe someone on the list could tell me under what general
conditions this assertion is expected to fail.

Thanks,
    Michael