Paperweight 1.20.4 custom biome

CustomBiome.kt

val biomeEffect =BiomeSpecialEffects.Builder()
    .skyColor(8103167)
    .fogColor(12638463)
    .waterColor(4159204)
    .waterFogColor(329011)
    .grassColorOverride(16747750)
    .build()

val craftServer = Bukkit.getServer() as CraftServer
val dedicatedServer = craftServer.server

val customKey = ResourceKey.create(Registries.BIOME, ResourceLocation("custom", "myCustomBiomeName"))
val writeableRegistry = dedicatedServer.registryAccess().registryOrThrow(Registries.BIOME) as WritableRegistry<Biome>
val customBiome = BiomeBuilder()
    .downfall(0.8F)
    .temperature(0.4F)
    .hasPrecipitation(false)
    .specialEffects(biomeEffect)
    .mobSpawnSettings(MobSpawnSettings.EMPTY)
    .generationSettings(BiomeGenerationSettings.EMPTY)
    .build()

runCatching {
    val frozenField = MappedRegistry::class.java.getDeclaredField("l")
    frozenField.isAccessible = true
    frozenField.set(writeableRegistry, false)

    val unregisteredIntrusiveHolders = MappedRegistry::class.java.getDeclaredField("m")
    unregisteredIntrusiveHolders.isAccessible = true
    unregisteredIntrusiveHolders.set(writeableRegistry, IdentityHashMap<ResourceKey<Biome>, Holder.Reference<Biome>>())

    writeableRegistry.createIntrusiveHolder(customBiome)
    writeableRegistry.register(customKey, customBiome, Lifecycle.stable())
    unregisteredIntrusiveHolders.set(writeableRegistry, null)
 
    frozenField.isAccessible = true
    frozenField.set(writeableRegistry, true)
}.onFailure { it.printStackTrace() }

// set the biome
val world = Bukkit.getWorld("world")!!
val craftChunk = world.getChunkAt(0, 0) as CraftChunk
val biomeAccess = craftChunk.getHandle(ChunkStatus.BIOMES)
biomeAccess.setBiome(0, 0, 0, Holder.direct(customBiome))