getTileUrlFunction() {
    return Object.getPrototypeOf(this).tileUrlFunction === this.tileUrlFunction
      ? this.tileUrlFunction.bind(this)
      : this.tileUrlFunction;
  }
Deprecated.  Use an ImageTile source instead.
Return the tile URL function of the source.
@return {import("../Tile.js").UrlFunction} TileUrlFunction
@api