[Zope] finding a unique id

[Tony Lownds]

How would one find a unique id in a folder. I have tried this DTML method:

<!--#var "'id%04d'%_.int(_.max(_.filter(lambda s:s[-2]=='id',_['objectIds'])+['id0000'])[2:])"-->

but _.filter is not defined. ANybody got any ideas?

-Tony