getPoint(index) {
    const n = this.flatCoordinates.length / this.stride;
    if (index < 0 || n <= index) {
      return null;
    }
    return new Point(
      this.flatCoordinates.slice(
        index * this.stride,
        (index + 1) * this.stride,
      ),
      this.layout,
    );
  }
Return the point at the specified index.
@param {number} index Index.
@return {Point} Point.
@api