[web2py] Subclass navbar() ?

[pbreit]

I can't seem to figure out the correct way to subclass navbar(). Does this 
look close?

=== db.y ==
from gluon.tools import *

class MyAuth(Auth):

    def __init__(self, environment, db): 
        pass
        
    def navbar(self,prefix='Welcome',action=None):
        ...
        return bar

auth = MyAuth(globals(),db)