How to search data and show like this,all the fields in result are connected by dot?

[jin_liu]

i found this when discover es data by kibana,all the fields are connected by dot,i wonder how to make this by es dsl?

{
  "_index": "zk_mysql_log-2022_08",
  "_type": "_doc",
  "_id": "DoEekIIBmO8s27BbCb_1",
  "_version": 1,
  "_score": null,
  "fields": {
    "agent.version.keyword": [
      "7.12.0"
    ],
    "zeek.mysql.success": [
      false
    ],
    "event.category": [
      "database",
      "network"
    ],
    "host.name.keyword": [
      "localhost.localdomain"
    ]
  },
  "sort": [
    1660135911000
  ]
}