[Zope] Will the inheritance relationship will be preserved after export/import?

[iap_y2fun.com]

Hi,
Suppose Product P1 is a subclass of Product P,
and M is a method of P, so that we can call both P.M and P1.M
Then,
P and P1 were exported from Data1.fs (Host A) ,
and imported to Data2.fs (Host B).

Now, let's move to the Host B, and modified the content of M.
and create an instance of Product P as p and Product P1 as p1.
It should be that p.M and p1.M execute the same code
(new content o f M).
But it is not.
p1.M execute the old code of M which is the same as it used to
be in Host A.
The interitance relationship seems broken after export/import
between different ZODB.
How can I rebuid the relationship between P and P1?

Thanks.
Iap