如何从chapel中的记录返回json字符串?

我有一些DTO记录定义为

record NodeDTO{
  var id: int,
      name: string,
      community: int;
}

record LinkDTO {
  var source: int,
      target: int,
      strength: real;
}

record GraphDTO {
  var nodes:[1..0] NodeDTO,
      links:[1..0] LinkDTO;
  proc init() {}
}

proc Graph.DTO() {
  var dto = new GraphDTO();
  for key in this.verts.keys {
    dto.nodes.push_back(new NodeDTO(id=this.verts.get(key), name=key, community=1));
    for nbs in this.neighbors(key).keys {
      dto.links.push_back(new LinkDTO(source=this.verts.get(key), target=this.verts.get(nbs), strength=1.0));
    }
  }
  return dto;
}

但是当我 writeln(dto) 我得到

(nodes = (id = 7, name = yondu, community = 1) (id = 1, name = star lord, community = 1) (id = 5, name = rocket, community =
 1) (id = 4, name = drax, community = 1) (id = 8, name = nebula, community = 1) (id = 3, name = groot, community = 1) (id = 2, name = gamora,
community = 1) (id = 6, name = mantis, community = 1), links = (source = 7, target = 8, strength = 1.0) (source = 1, target = 4, strength = 1.
0) (source = 1, target = 3, strength = 1.0) (source = 1, target = 2, strength = 1.0) (source = 5, target = 6, strength = 1.0) (source = 4, tar
get = 5, strength = 1.0) (source = 3, target = 4, strength = 1.0) (source = 2, target = 4, strength = 1.0) (source = 6, target = 7, strength =
 1.0) (source = 6, target = 8, strength = 1.0))

它不能正确地解释为json。我将此发送到浏览器 Chrest 作为一个网络服务器。如何让它在字符串周围加上引号,并完成所有好的jsony操作?