def _ensure_value_is_in_objects(self,val):
        """
        Make sure that the provided value is present on the objects list.
        Subclasses can override if they support multiple items on a list,
        to check each item instead.
        """
        if not (val in self.objects):
           self.objects.append(val)
Make sure that the provided value is present on the objects list.
        Subclasses can override if they support multiple items on a list,
        to check each item instead.