Not parse tree structured data

[phoenix91love]

Code Example has error
JsonSerializer.options = JsonSerializerOptions(types: [
UserType(Node.new),
]);
var json = '''{
"id": 1,
"parentId": null,
"name": "Root",
"children": [
{
"id": 2,
"parentId": 1,
"name": "Folder A",
"children": [
{"id": 4, "parentId": 2, "name": "File 1"},
{"id": 5, "parentId": 2, "name": "File 2"}
]
},
{
"id": 3,
"parentId": 1,
"name": "Folder B",
"children": [
{"id": 6, "parentId": 3, "name": "File 3"},
{"id": 7, "parentId": 3, "name": "File 3"}
]
}
]
}''';

var data= deserialize(json);