getTileSize(z) {
    if (this.tileSize_) {
      return this.tileSize_;
    }
    return this.tileSizes_[z];
  }
Get the tile size for a zoom level. The type of the return value matches the
`tileSize` or `tileSizes` that the tile grid was configured with. To always
get an {@link import("../size.js").Size}, run the result through {@link module:ol/size.toSize}.
@param {number} z Z.
@return {number|import("../size.js").Size} Tile size.
@api