[Zope] How to use 'in' ?

Hi, I try to use Zope. After reading the documentation, I don't understand how to use the tag 'in'. Here is the problem: The variable 'adr' is initialise to 'Donnees/Lab' (a folder) <!--in adr--> return the message 'Strings are not allowed as input to the in tag.' <!--in Donnees--> return the message 'Type error : hasattr, argument 2: expected string, int found' Can you help me ? Thank you.