this is what I tried:
> python web2py.py -S welcome -M -N
....
>>> countries = {'ti': 'Timor Leste', 'vn': 'Vietnam','in': 'India','kr':
>>> 'Korea','cn': 'China'}
>>> db.define_table('address', Field('country'),
>>> Field('state'),Field('street_address'))
>>> db.address.country.requires=IS_IN_SET(countries, zero=None)
>>> db.define_table('personal_address', db.auth_user, db.address)
>>> print db.address.country.requires is db.personal_address.country.requires
True
Look to me the requires is inherited. Perhaps I am missing something
