[Zope] newbie:cookie expiry problem

[prabuddha ray]

This may be very silly plz help
I gave this cookie expiry statement in a python script:

RESPONSE.expireCookie('login')

return context.REQUEST.RESPONSE.redirect('index_html')

but when i checked the cookie values in request page, it wasn't removed. 
the last redirect still worked.

when i put an if like this :
if (RESPONSE.expireCookie('login'))

return context.REQUEST.RESPONSE.redirect('index_html')

redirect didn't work. where am i wrong?
all the files are in same folder

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