getTile(z, x, y, pixelRatio, projection) {
    return abstract();
  }
@abstract
@param {number} z Tile coordinate z.
@param {number} x Tile coordinate x.
@param {number} y Tile coordinate y.
@param {number} pixelRatio Pixel ratio.
@param {import("../proj/Projection.js").default} projection Projection.
@return {TileType|null} Tile.