json_schema: {
      "$schema": "http://json-schema.org/draft-04/schema#",
      "definitions": {
          "advertisement": {
              "type": "object",
              "properties": {
                  "id": {
                      "type": "string"
                  }
              },
              "required": [
                  "id"
              ]
          }
      },
      "type": "array",
      "items": {
          "$ref": "#/definitions/advertisement"
      },
      "additionalProperties": false
  }