json_schema: {
      "description": "A generic link between two (or more) entitites",
      "properties": {
          "end_date": {
              "description": "The date on which the relationship ended",
              "format": "date",
              "sortIndex": 70,
              "title": "End date",
              "type": [
                  "string",
                  "null"
              ]
          },
          "id": {
              "hidden": true,
              "title": "ID",
              "type": "integer"
          },
          "start_date": {
              "description": "The date on which the relationship began",
              "format": "date",
              "sortIndex": 71,
              "title": "Start date",
              "type": [
                  "string",
                  "null"
              ]
          }
      },
      "title": "A link between entities",
      "type": "object"
  }