276   selection: ::

   276   selection (one standard place in in vreg.py) : ::

   277 

   277 

   278     from cubicweb.common.selectors import traced_selection

   278     def possible_objects(self, registry, *args, **kwargs):

   279     with traced_selection():

   279         """return an iterator on possible objects in a registry for this result set

   280         comp = self.vreg.select_object('contentnavigation', 'wfhistory',

   280 

   281                                        self.req, rset, context='navcontentbottom')

   281         actions returned are classes, not instances

   282 

   282         """

   283   This will yield additional WARNINGs, like this: ::

   283         from cubicweb.selectors import traced_selection

   284         with traced_selection():

   285             for vobjects in self.registry(registry).values():

   286                 try:

   287                     yield self.select(vobjects, *args, **kwargs)

   288                 except NoSelectableObject:

   289                     continue

   290 

   291   Don't forget the 'from __future__ improt with_statement' at the

   292   module top-level.

   293 

   294   This will yield additional WARNINGs, like this:

   295   ::