我正在尝试使用groovy脚本将以下JSON文件转换为XML文件

{
    "quiz": {
        "sport": {
            "q1": {
                "question": "Which one is correct team name in NBA?",
                "options": ["New York Bulls","Los Angeles Kings","Golden State Warriros",
                    "Huston Rocket"],
                "answer": "Huston Rocket"
            }
        },
        "maths": {
            "q1": {
                "question": "5 + 7 = ?",
                "options": ["10","11","12",
                    "13"],
                "answer": "12"
            },
            "q2": {
                "question": "12 - 8 = ?",
                "options": ["1","2","3",
                    "4"
                ],
                "answer": "4"
            }
        }
    }
}

但在执行代码后出现此错误错误部分

Caught: groovy.lang.MissingPropertyException: No such property: question for class: java.lang.String
groovy.lang.MissingPropertyException: No such property: question for class: java.lang.String
    at json_xml$_run_closure1$_closure2$_closure3$_closure5.doCall(json.xml.groovy:13)
    at json_xml$_run_closure1$_closure2$_closure3.doCall(json.xml.groovy:12)
    at json_xml$_run_closure1$_closure2$_closure3.doCall(json.xml.groovy)
    at json_xml$_run_closure1$_closure2.doCall(json.xml.groovy:12)
    at json_xml$_run_closure1$_closure2.doCall(json.xml.groovy)
    at json_xml$_run_closure1.doCall(json.xml.groovy:11)
    at json_xml$_run_closure1.doCall(json.xml.groovy)
    at json_xml.run(json.xml.groovy:10)

有人能告诉我我哪里出错了吗？这将是非常有帮助的，因为我即将到来的项目主要是使用Groovy开发这种类型的转换脚本。我是编码领域的新手。
我写的剧本是这样的。

import groovy.json.JsonSlurper
import groovy.xml.MarkupBuilder
import java.io.*
java.io.StringWriter
def f1 = new File("C:/Users/lenovo/Desktop/1b adangals/groovy/JSON-XML/example_2.json")
def json = new JsonSlurper().parse(f1)
def writer = new StringWriter()
def xmlf = new MarkupBuilder(writer)
xmlf.quiz{
    subject('sport')
{q1{json.quiz.sport.q1.collect{s,t->
    question(t.question)
    options(t.options)
    answer(t.answer) }}
subject('maths')
{q1{json.quiz.maths.q1.collect{q,r->
    question(r.q1.question)
}}}   }
}   
println writer.toString()

我预期的结果会是这样

<quiz>
     <subject>sport</subject>
       <q1>
         <question>krlsfnwlkf</question>
         <options>NYB,LAK,GSW,HR</options>
         <answer>fsfwrfw</answer>
       </q1>
     <subject> maths</subject>
        <q1>
          <question>csfwf</question>
          <options>cadfa</options>
        </q1>
</quiz>