def _insert_element_before(self, node: Node, ref_node: Node) -> Node:
if node.parentNode:
node.parentNode.removeChild(node)
self._children.insert(self.index(ref_node), node)
node._parent = self
return node
def _remove_child(self, node: Node) -> Node:
if node not in self._children:
raise ValueError('node to be removed is not a child of this node.')
self._children.remove(node)
node._parent = None
return node
def _append_element(self, node: Node) -> Node:
if node.parentNode:
node.parentNode.removeChild(node)
self._children.append(node)
node._parent = self
return node
