json_schema: {
      "additionalProperties": false,
      "properties": {
          "grades": {
              "items": {
                  "additionalProperties": false,
                  "properties": {
                      "deleted_at": {
                          "format": "date-time",
                          "type": [
                              "string",
                              "null"
                          ]
                      },
                      "lesson_id": {
                          "type": "string"
                      },
                      "mark": {
                          "type": "number"
                      },
                      "skill_id": {
                          "type": "number"
                      },
                      "student_id": {
                          "type": "number"
                      }
                  },
                  "required": [
                      "mark",
                      "skill_id",
                      "lesson_id",
                      "student_id",
                      "deleted_at"
                  ],
                  "type": "object"
              },
              "type": "array"
          },
          "meta": {
              "additionalProperties": false,
              "properties": {
                  "timestamp": {
                      "_format": "date-time",
                      "type": "string"
                  }
              },
              "required": [
                  "timestamp"
              ],
              "type": "object"
          }
      },
      "required": [
          "grades",
          "meta"
      ],
      "type": "object"
  }