computeExtent(extent) {
    const flatCoordinates = this.flatCoordinates;
    const radius = flatCoordinates[this.stride] - flatCoordinates[0];
    return createOrUpdate(
      flatCoordinates[0] - radius,
      flatCoordinates[1] - radius,
      flatCoordinates[0] + radius,
      flatCoordinates[1] + radius,
      extent,
    );
  }
@param {import("../extent.js").Extent} extent Extent.
@protected
@return {import("../extent.js").Extent} extent Extent.
@override