用python中的iterate对象创建一个带有一组树的iterate对象

class TreeNode:
    def __init__(self, value):
        self.value = value
        self.children = []
    
    def add_child(self, child):
        self.children.append(child)


class TreeIterator:
    def __init__(self, root):
        self.stack = [root]

    def __iter__(self):
        return self

    def __next__(self):
        if not self.stack:
            raise StopIteration

        node = self.stack.pop()
        self.stack.extend(reversed(node.children))
        return node.value


# 创建一个树结构
root = TreeNode('A')
b = TreeNode('B')
c = TreeNode('C')
d = TreeNode('D')
e = TreeNode('E')
f = TreeNode('F')
g = TreeNode('G')

root.add_child(b)
root.add_child(c)
b.add_child(d)
b.add_child(e)
c.add_child(f)
c.add_child(g)

# 创建树的迭代器对象
tree_iterator = TreeIterator(root)

# 遍历树的迭代器对象
for value in tree_iterator:
    print(value)