function extendRings(extent, rings) {
  for (let i = 0, ii = rings.length; i < ii; ++i) {
    extendCoordinates(extent, rings[i]);
  }
  return extent;
}
@param {Extent} extent Extent.
@param {Array<Array<import("./coordinate.js").Coordinate>>} rings Rings.
@return {Extent} Extent.