def siblings(self, node):
        """ Returns a :class:`QuerySet` of all siblings of a given
            :class:`CTENode` `node`.

            :param node: a :class:`CTENode` whose siblings are required.

            :returns: A :class:`QuerySet` of all siblings of the given `node`.
        """
        # We need to read the _cte_node_parent* attributes, so ensure they
        # exist.
        self._ensure_parameters()
        # We need to construct: filter(parent = node.parent_id)
        return self.filter(
            **{
                self.model._cte_node_parent: getattr(
                    node, self.model._cte_node_parent_attname
                )
            }
        ).exclude(id=node.id)