Python GraphQL如何声明自引用石墨烯对象类型

from graphene import ObjectType, String, List, Field

class TreeNode(ObjectType):
    name = String()
    children = List(lambda: TreeNode)

class Query(ObjectType):
    tree = Field(TreeNode)

    def resolve_tree(self, info):
        # 在这里编写获取树节点数据的逻辑
        # 返回一个树节点对象
        return TreeNode(name="Root", children=[
            TreeNode(name="Node 1", children=[
                TreeNode(name="Node 1.1", children=[]),
                TreeNode(name="Node 1.2", children=[]),
            ]),
            TreeNode(name="Node 2", children=[]),
        ])

from graphene import Schema

schema = Schema(query=Query)

result = schema.execute('''
    query {
        tree {
            name
            children {
                name
                children {
                    name
                }
            }
        }
    }
''')

print(result.data)