{
    "persistent_object": {
      "double_sided_image_urls ": [
        [
          "http://example.com/omote1.png",
          "http://example.com/ura1.png"
        ],
        [
          "http://example.com/omote2.png",
          "http://example.com/ura2.png"
        ]
      ]
    }
  }