How to return hierarchical JSON from a query in ISG SOA Suite

Is it possible generate a hierarchical JSON output in ISG? For example (employees within departments):

{
  "departments":[
    {
      "department":{
        "department_name":"DEV",
        "department_no":70,
        "employees":[
          {
            "employee_number":9000,
            "employee_name":"JONES",
            "salary":1000
          },
          {
            "employee_number":9001,
            "employee_name":"SMITH",
            "salary":2000
          }
        ]
      }
    },

I can write a SQL query like this:

select a.invoice_id, invoice_num, 
      cursor(select line_number, description
      from ap_invoice_lines_all l where l.invoice_id=a.invoice_id) lines
    from ap_invoices_all a
    where invoice_id=145054;

But how do I actually put that into ISG so that I get the hierarchical JSON produced. It needs to go into a package somehow and I cannot figure that part out.