code: function (renderable) {
                  if (!(renderable instanceof WorldWind.Placemark)) {
                      throw new ArgumentError(
                          Logger.logMessage(Logger.LEVEL_SEVERE, "GeoJSONExporter", "exportPlacemark",
                              "invalidTypeOfRenderable"));
                  }
  
                  var sb = '{';
                  sb = sb + '"' + GeoJSONConstants.FIELD_TYPE + '":"' + GeoJSONConstants.TYPE_POINT + '",';
                  sb = sb + '"' + GeoJSONConstants.FIELD_COORDINATES + '":';
                  sb = sb + '[' + renderable.position.longitude + ',' + renderable.position.latitude + ']';
                  sb = sb + '}';
                  return sb;
              }
docs: Exports a [Placemark]{@link Placemark} in GeoJSON format of type Point.
  @param {Placemark} renderable The Placemark object.
  @throws {ArgumentError} If the specified argument is null or undefined.
  @returns {String} GeoJSON format.