{
  "type":"seq",
  "sequence":
  [
    {
      "type":"map",
      "title":"Level 1 item",
      "mapping":
      {
        "field1":
        {
          "type":"str"
        },
        "field2":
        {
          "type":"str"
        },
        "sublevel":
        {
          "type":"idref",
          "idref":"bloblist"
        }
      },
      "user_key":"sublevel"
    }
  ]
}