What kind of Spec Array to Output key value pairs where key is a data value in input array and value is array

[AKulkarniZT]

Input:

"aggregations:"{
    "masterId" : {
      "doc_count_error_upper_bound" : 0,
      "sum_other_doc_count" : 0,
      "buckets" : [
        {
          "key" : "1Q52",
          "doc_count" : 3,
          "serialNumbers" : {
            "doc_count_error_upper_bound" : 0,
            "sum_other_doc_count" : 0,
            "buckets" : [
              {
                "key" : "3R24Z3",
                "count" : 1
              },
              {
                "key" : "526GA2",
                "count" : 1
              },
              {
                "key" : "873XHE",
                "count" : 1
              }
            ]
          }
        }
      ]
    }
  }

Spec: Trying to figure this out

Desired Output:

{"1Q52": ["3R24Z3", "526GA2", "873XHE"]}

My current Spec array is

[{
        "operation": "shift",
        "spec": {
            "aggregations": {
                "masterId": {
                    "buckets": {
                        "*": {
                            "key": "key",
                            "serialNumbers": {
                                "buckets": {
                                    "*": {
                                        "key": "key"
                                    }
                                }
                            }
                        }
                    }
                }
            }
        }
}]

and my current output is

{"key":["1Q52","3R24Z3", "526GA2", "873XHE"]}

What kind of spec array could give me the desired output?

[AKulkarniZT]

Got an answer here