json_schema: {
      "$schema": "http://json-schema.org/draft-04/schema#",
      "definitions": {
          "B.B": {
              "properties": {
                  "b": {}
              },
              "required": [
                  "b"
              ],
              "type": "object"
          },
          "C.C": {
              "properties": {
                  "c": {
                      "$ref": "#/definitions/B.B"
                  }
              },
              "required": [
                  "c"
              ],
              "type": "object"
          }
      },
      "properties": {
          "d": {
              "$ref": "#/definitions/C.C"
          }
      },
      "required": [
          "d"
      ],
      "type": "object"
  }