如何获取按谱系关联的值的索引列表？[R]

class TreeNode:
    def __init__(self, value):
        self.value = value
        self.children = []
        self.parent = None

    def add_child(self, child_node):
        self.children.append(child_node)
        child_node.parent = self

def get_ancestors(node):
    ancestors = []
    current_node = node.parent
    while current_node is not None:
        ancestors.append(current_node.value)
        current_node = current_node.parent
    return ancestors[::-1]  # Reverse the list to get the correct order

# 示例用法
root = TreeNode('root')
child1 = TreeNode('child1')
child2 = TreeNode('child2')
grandchild = TreeNode('grandchild')

root.add_child(child1)
root.add_child(child2)
child1.add_child(grandchild)

print(get_ancestors(grandchild))  # 输出: ['root', 'child1']