If the form contains a listbox, the corresponding "List Method" will be most of the time contentValues.
Generally we want to display sub documents. If you are not displaying
sub objects but related objects, you will need to define another List Method,
often category accessor, like getSourceProjectRelatedValueList.
In "default parameters" you have to specify "checked_permission | View" so that
contentValues does not display sub-documents on which the user does not have the
searchFolder method uses SQL catalog to get documents so if the number of
subdocuments is known to be small, it's usually faster to use contentValues
directly; contentValues gets documents from Zope's object database.