getRequestUrl_(tileCoord, tileExtent, pixelRatio, projection, params) {
    const urls = this.urls;
    if (!urls) {
      return undefined;
    }
    let url;
    if (urls.length == 1) {
      url = urls[0];
    } else {
      const index = modulo(tileCoordHash(tileCoord), urls.length);
      url = urls[index];
    }

    return getImageSrc(
      tileExtent,
      (
        this.tileGrid || this.getTileGridForProjection(projection)
      ).getResolution(tileCoord[0]),
      pixelRatio,
      projection,
      url,
      params,
      this.serverType_,
    );
  }
@param {import("../tilecoord.js").TileCoord} tileCoord Tile coordinate.
@param {import("../extent.js").Extent} tileExtent Tile extent.
@param {number} pixelRatio Pixel ratio.
@param {import("../proj/Projection.js").default} projection Projection.
@param {Object} params Params.
@return {string|undefined} Request URL.
@private