How to use the prismarine-provider-anvil.level.writeLevel function in prismarine-provider-anvil

let seed
  let regionFolder
  if (worldFolder) {
    regionFolder = worldFolder + '/region'
    try {
      await fsStat(regionFolder)
    } catch (err) {
      await fsMkdir(regionFolder)
    }

    try {
      const levelData = await level.readLevel(worldFolder + '/level.dat')
      seed = levelData['RandomSeed'][0]
    } catch (err) {
      seed = newSeed
      await level.writeLevel(worldFolder + '/level.dat', { 'RandomSeed': [seed, 0] })
    }
  } else { seed = newSeed }
  generation.options.seed = seed
  generation.options.version = version
  serv.emit('seed', generation.options.seed)
  const generationModule = generations[generation.name] ? generations[generation.name] : require(generation.name)
  serv.overworld = new World(generationModule(generation.options), regionFolder)
  serv.netherworld = new World(generations['nether'](generation.options))
  // serv.endworld = new World(generations["end"]({}));

  // WILL BE REMOVED WHEN ACTUALLY IMPLEMENTED
  serv.overworld.blockEntityData = {}
  serv.netherworld.blockEntityData = {}
  serv.overworld.portals = []
  serv.netherworld.portals = []
  /// ///////////