def dump_is_last(self, obj):
        """Dump the boolean stating if the child in the relation is last.

        Dumps `None` for parent serialization.
        """
        if self._is_child(obj) and isinstance(obj, PIDNodeOrdered):
            if obj.children.count() > 0:
                return obj.children.ordered('asc').all()[-1] == \
                    self.context['pid']
            elif obj.draft_child:
                return obj.draft_child == self.context['pid']
            else:
                return True
        else:
            return None