getPolygons() {
    const layout = this.layout;
    const flatCoordinates = this.flatCoordinates;
    const endss = this.endss_;
    const polygons = [];
    let offset = 0;
    for (let i = 0, ii = endss.length; i < ii; ++i) {
      const ends = endss[i].slice();
      const end = ends[ends.length - 1];
      if (offset !== 0) {
        for (let j = 0, jj = ends.length; j < jj; ++j) {
          ends[j] -= offset;
        }
      }
      const polygon = new Polygon(
        flatCoordinates.slice(offset, end),
        layout,
        ends,
      );
      polygons.push(polygon);
      offset = end;
    }
    return polygons;
  }
Return the polygons of this multipolygon.
@return {Array<Polygon>} Polygons.
@api