[Zope] where __changed__() method defined ?

[Chihiro Kuraya]

Greetings,

I'm making a Zope product 
imitating some sample products.

I encountered codes like "self.__changed__(1)",
notifying ZODB that this object has changed.

I wornder where the method __changed__() defined ?
I greped Zope source code under lib/python/,
but not found.


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Chihiro Kuraya