fn create_flat(
world_path: Option<&Path>,
config: &WorldGeneratorConfigData,
seed: i64,
thread_pool: &ThreadPool,
) -> Result<GeneratorOutput, String>fn create_flat(
world_path: Option<&Path>,
config: &WorldGeneratorConfigData,
seed: i64,
thread_pool: &ThreadPool,
) -> Result<GeneratorOutput, String>