function handleResponse(format, data) {
    return format.callback(data);
  }
Asynchronously determines what features, if any, are located at a given longitude and latitude within
a tile.

@param {number} x The tile X coordinate.
@param {number} y The tile Y coordinate.
@param {number} level The tile level.
@param {number} longitude The longitude at which to pick features.
@param {number} latitude  The latitude at which to pick features.
@return {Promise<ImageryLayerFeatureInfo[]>|undefined} A promise for the picked features that will resolve when the asynchronous
                  picking completes.  The resolved value is an array of {@link ImageryLayerFeatureInfo}
                  instances.  The array may be empty if no features are found at the given location.
                  It may also be undefined if picking is not supported.