使用XSuperObject将JSON提取为字符串

Question

是否可以从此JSON中提取“提取物”中的内部JSON作为字符串？

{
   ID: "4_06052019065429_2772",
   document_type: "test",
   upload_date: "2019-05-06 06:54:29",
   original_filename: "XYZ",
   hash: "F577AAA0993BC11762670DA0A8C14FB6.pdf",
   status: "extracted",
   extractions: {
            elements: [
                 { element: "A",
                   extraction: "B",
                   score: 95.635139
                 },
                 {
                   element: "B",
                   extraction: "VVV",
                   score: 99.963783
                 },
                 {
                   element: "Z",
                   extraction: "XYZ2",
                   score: 99.979317
                 }
                 ],
                 status: "OK"
   },(...)

我尝试将其强制转换为字符串，但返回无效 可以使用XSuperObject吗？

这将返回无效的转换

s : string;
s:= super_object.A['documents'].O[i].S['extractions'];