Cesium3DTileset splitDirection

CesiumJS
1

Hello,
I’m trying to replicate this example in my app https://sandcastle.cesium.com/?src=Imagery%20Layers%20Split.html
The code of my sandcastle is:

// Grant CesiumJS access to your ion assets
Cesium.Ion.defaultAccessToken = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJqdGkiOiJkZDg0MDZjYy00MzJlLTQzM2UtOTg3OS1kNjA0ODZmMDA3YmEiLCJpZCI6MzQzOTUsImlhdCI6MTYwMDI0Nzc0NX0.U1eekATx6rZllZj6XO8gHtEQyWnMwayyazZek2tWdvs";

const viewer = new Cesium.Viewer("cesiumContainer", {
  terrainProvider: new Cesium.CesiumTerrainProvider({
    url: Cesium.IonResource.fromAssetId(1),
  }),
});
viewer.scene.globe.depthTestAgainstTerrain = true;

const tileset = viewer.scene.primitives.add(
  new Cesium.Cesium3DTileset({
    url: Cesium.IonResource.fromAssetId(152576),
  })
);
tileset.splitDirection = Cesium.SplitDirection.RIGHT;
(async () => {
  try {
    await tileset.readyPromise;
    await viewer.zoomTo(tileset);

    // Apply the default style if it exists
    var extras = tileset.asset.extras;
    if (
      Cesium.defined(extras) &&
      Cesium.defined(extras.ion) &&
      Cesium.defined(extras.ion.defaultStyle)
    ) {
      tileset.style = new Cesium.Cesium3DTileStyle(extras.ion.defaultStyle);
    }
  } catch (error) {
    console.log(error);
  }
})();

But I get this error:
Uncaught TypeError: Cesium.SplitDirection.RIGHT

Can someone help me?
Thank you