code: def _populate(self):
          
          if not self._populated:
              logging.debug("Populating lazy list %d (%s)" % (id(self), self.__class__.__name__))
              try:
                  self.populate()
                  self._populated = True
              except Exception, e:
                  logging.debug("Currently unable to populate lazy list: %s" % e)
docs: Populate this list by calling populate(), but only once.