[SQLObject] Reference to one of multiple tables

I'm stuck at a part of my program, but I'm not sure if this is the right
place to ask. Excuses if it's not.

I have a DVD object which can have different statusses, like "on loan",
"sold", etc... A dvd can only have 1 status at the time, but I'm confused
about how to link it to 1 table only so I can access the correct status
with dvd.status .

Here's an example:

class DVD(SQLObject):
    status = ???? # Should be sold or onloan data
    # ... special "dvd" data

class Sold(SQLObject):
    dvd = ForeignKey('DVD')
    # ... special "sold" data

class OnLoan(SQLObject):
    dvd = ForeignKey('DVD')
    # ... special "on loan" data

Greets,
Timo