json_schema: {
      "additionalProperties": false,
      "description": "A first_visit GA4 event.",
      "properties": {},
      "self": {
          "format": "jsonschema",
          "name": "first_visit",
          "vendor": "com.google.ga4",
          "version": "1-0-0"
      },
      "type": "object"
  }