code: function writeLineStringGeometry_(geometry) {
    if (geometry instanceof olGeomLineString) {
      const flatCoordinates = geometry.getFlatCoordinates();
      const stride = geometry.getStride();
      const end = flatCoordinates.length;
      return `l(${this.encodeCoordinates_(flatCoordinates, stride, 0, end)})`;
    }
    return null;
  }
docs: Encode a {@link import("ol/geom/LineString.js").default} geometry into a logical sequence of
  characters.
  @param {Geometry} geometry Geometry.
  @return {?string} Encoded geometry.
  @private
  @hidden
  @this {FeatureHash}