code: function (renderable) {
                  if (!renderable) {
                      throw new ArgumentError(
                          Logger.logMessage(Logger.LEVEL_SEVERE, "GeoJSONExporter", "exportRenderable",
                              "missingRenderable"));
                  }
  
                  if (renderable instanceof WorldWind.Placemark) {
                      return this.exportPlacemark(renderable);
                  }
                  else if (renderable instanceof WorldWind.SurfacePolyline) {
                      return this.exportSurfacePolyline(renderable);
                  }
                  else if (renderable instanceof WorldWind.SurfacePolygon) {
                      return this.exportSurfacePolygon(renderable);
                  }
                  else if (renderable instanceof WorldWind.SurfaceEllipse) {
                      return this.exportSurfaceEllipse(renderable);
                  }
                  else if (renderable instanceof WorldWind.SurfaceCircle) {
                      return this.exportSurfaceCircle(renderable);
                  }
                  else if (renderable instanceof WorldWind.SurfaceRectangle) {
                      return this.exportSurfaceRectangle(renderable);
                  }
                  else if (renderable instanceof WorldWind.SurfaceSector) {
                      return this.exportSurfaceSector(renderable);
                  }
                  else if (renderable instanceof WorldWind.Path) {
                      return this.exportPath(renderable);
                  }
                  else if (renderable instanceof WorldWind.Polygon) {
                      return this.exportPolygon(renderable);
                  }
                  else {
                      Logger.log(Logger.LEVEL_WARNING, "Export renderable not implemented: " + renderable);
                      return null;
                  }
              }
docs: Exports a [Renderable]{@link Renderable} in GeoJSON format.
  @param {Renderable} renderable The renderable to export.
  @throws {ArgumentError} If the specified renderable is null or undefined.
  @returns {String} GeoJSON format.