function encodePolygonGeometry(geom) {
  const array = [];
  const rings = geom.getLinearRings();
  for (let i = 0, ii = rings.length; i < ii; ++i) {
    array.push('(' + encodeLineStringGeometry(rings[i]) + ')');
  }
  return array.join(',');
}
@param {Polygon} geom Polygon geometry.
@return {string} Coordinates part of Polygon as WKT.