constructor() {
    super();

    /**
     * The maximum dimensions of the thumbnail to render, in pixels. If only one
     * number is passed, it is used as the maximum, and the other dimension is
     * computed by proportional scaling. Otherwise, a pair of numbers in the
     * format [width, height].
     * @export {number|string|!Array<number>|undefined}
     */
    this.dimensions;

    /**
     * The geospatial region of the image to render. By default, the whole
     * image. If defined, either an array in the format [east, south, west,
     * north] or else a GeoJSON geometry.
     * @export {!Array<number>|!ee.data.GeoJSONGeometry|undefined}
     */
    this.region;

    /**
     * The base name of the thumbnail, only used for zipped GeoTIFF.
     * @export {string|undefined}
     */
    this.name;
  }
An object describing the parameters for generating a thumbnail image.
Consists of all parameters of ee.data.ImageVisualizationParameters as well as
additional fields.
@see ee.data.ImageVisualizationParameters
@record @struct