如何在 flatbuffers cpp 中定义树结构？

Question

// ptree.fbs
namespace MyApp;

table PTree {
    name:string;
    value:string;
    type:string;
    children:[Ptree];
}

root_type PTree;

运行

./../flatc --cpp ptree.fbs

时，出现如下错误

error: type referenced but not defined (check namespace): Ptree, originally at: ptree.fbs:7

我应该如何定义

PTree

以便它是递归的？