convertxml 无法解析 子 tag 中的子 tag element 数据

xml 数据: 
 
<?xml version="1.0" encoding="GBK"?> 
  <send_confirm_code> 
  <ret code="0" msg="注册成功"/> 
  </send_confirm_code> 
  convertOptions: 
let options: convertxml.ConvertOptions = { 
  trim: true, 
  ignoreDeclaration: true, 
  declarationKey: “_declaration”, 
  instructionKey: “_instruction”, 
  attributesKey: “_attributes”, 
  textKey: “_text”, 
  cdataKey: “_cdata”, 
  doctypeKey: “_doctype”, 
  commentKey: “_comment”, 
  parentKey: “_parent”, 
  typeKey: “_type”, 
  nameKey: “_name”, 
  elementsKey: “_elements” 
} 
解析出来的对象里缺少 send_confirm_code 里的 element 数据