code: def pathFromItem(self, item, avatar):
          
          for subnav in self.children:
              subpath = subnav.pathFromItem(item, avatar)
              if subpath:
                  subpath.insert(0, self)
                  return subpath
          else:
              myItem = self.loadForAvatar(avatar)
              if myItem is item:
                  return [self]
          return []
docs: @param item: A thing that we linked to, and such.
  
          @return: a list of [child, grandchild, great-grandchild, ...] that
          indicates a path from me to the navigation for that item, or [] if
          there is no path from here to there.