code: function getChildren(tile) {
      return [
          [tile[0] * 2, tile[1] * 2, tile[2] + 1],
          [tile[0] * 2 + 1, tile[1] * 2, tile[2 ] + 1],
          [tile[0] * 2 + 1, tile[1] * 2 + 1, tile[2] + 1],
          [tile[0] * 2, tile[1] * 2 + 1, tile[2] + 1]
      ];
  }
docs: Get the 4 tiles one zoom level higher
  
  @name getChildren
  @param {Array<number>} tile
  @returns {Array<Array<number>>} tiles
  @example
  var tiles = getChildren([5, 10, 10])
  //=tiles