addParallel_(lat, minLon, maxLon, squaredTolerance, extent, index) {
    const lineString = this.getParallel_(
      lat,
      minLon,
      maxLon,
      squaredTolerance,
      index,
    );
    if (intersects(lineString.getExtent(), extent)) {
      if (this.parallelsLabels_) {
        const text = this.latLabelFormatter_(lat);
        if (index in this.parallelsLabels_) {
          this.parallelsLabels_[index].text = text;
        } else {
          this.parallelsLabels_[index] = {
            geom: new Point([]),
            text: text,
          };
        }
      }
      this.parallels_[index++] = lineString;
    }
    return index;
  }
@param {number} lat Latitude.
@param {number} minLon Minimal longitude.
@param {number} maxLon Maximal longitude.
@param {number} squaredTolerance Squared tolerance.
@param {import("../extent.js").Extent} extent Extent.
@param {number} index Index.
@return {number} Index.
@private