_updateImageryConfigurations() {
    const model = this._model;
    const imageryLayers = model.imageryLayers;
    const imageryConfigurations = this._imageryConfigurations;
    imageryConfigurations.length = imageryLayers.length;
    for (let i = 0; i < imageryLayers.length; i++) {
      const imageryLayer = imageryLayers.get(i);
      imageryConfigurations[i] = new ImageryConfiguration(imageryLayer);
    }
  }
Create one <code>ImageryConfiguration</code> object for each imagery
layer that appears in the model, and store them as the
<code>_imageryConfigurations</code>.