[Zope] How to use 'in' ?

[thilor]

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.