json_schema: {
      "$schema": "http://json-schema.org/draft-04/schema",
      "definitions": {
          "operation": {
              "enum": [
                  "insert",
                  "update",
                  "delete"
              ]
          }
      },
      "type": "object",
      "properties": {
          "operation": {
              "$ref": "#/definitions/operation"
          }
      },
      "required": [
          "operation"
      ],
      "additionalProperties": false
  }