json_schema: {
      "$schema": "http://json-schema.org/draft-07/schema#",
      "properties": {
          "subject": {
              "oneOf": [
                  {
                      "$ref": "#/definitions/first"
                  },
                  {
                      "$ref": "#/definitions/second"
                  }
              ]
          }
      },
      "definitions": {
          "first": {
              "type": "object",
              "properties": {
                  "discriminator": {
                      "const": "first"
                  },
                  "first": {
                      "type": "boolean"
                  }
              },
              "additionalProperties": false
          },
          "second": {
              "type": "object",
              "properties": {
                  "discriminator": {
                      "const": "second"
                  },
                  "second": {
                      "type": "boolean"
                  }
              },
              "additionalProperties": false
          }
      }
  }