我正在尝试访问spark elastic connect中输出的聚合部分。下面是一个例子，我需要访问 aggregations.buckets.key 在我的Dataframe中。有人能帮忙吗

{
  "hits": {
    "total": {
      "value": 5718,
      "relation": "eq"
    },
    "max_score": null,
    "hits": []
  },
  "aggregations": {
    "multiple_aggregates": {
      "doc_count_error_upper_bound": 0,
      "sum_other_doc_count": 2618,
      "buckets": [
        {
          "key": "-999999",
          "doc_count": 1,
          "count": {
            "value": 1
          }
        },
        {
          "key": "0",
          "doc_count": 1,
          "count": {
            "value": 1
          }
        }
      ]
    },
    "groupBy": {
      "value": 728
    }
  }
}