add() function on containers which check for existing id
add() function on containers which check for existing id

derFreitag/mockup,plone/mockup,domruf/mockup,plone/mockup,derFreitag/mockup,derFreitag/mockup,plone/mockup,domruf/mockup,termitnjak/mockup,termitnjak/mockup,domruf/mockup,domruf/mockup,termitnjak/mockup,derFreitag/mockup,termitnjak/mockup