[web2py] multiple 'requires'

[Larry Wapnitsky]

I'm trying to use the following in my applications, but only one works at a 
time:

db.ips.ipaddress.requires = IS_NOT_IN_DB(db, 'ips.ipaddress')
db.ips.ipaddress.requires = IS_IPV4()

How can I get them both to process?

Thank you,
Larry