You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: room_based_spawner.rs
    path of file: ./repos/rustrogueliketutorial/chapter-63-effects/src/map_builders
    
    the code of the file until where you have to start completion: use super::{MetaMapBuilder, BuilderMap, spawner};
use rltk::RandomNumberGenerator;

pub struct RoomBasedSpawner {}

impl MetaMapBuilder for RoomBasedSpawner {
    fn build_map(&mut self, rng: &mut rltk::RandomNumberGenerator, build_data : &mut BuilderMap)  {
        self.build(rng, build_data);
    }
}

impl RoomB
    
    fn build(&mut self, rng : &mut RandomNumberGenerator, build_data : &mut BuilderMap) {
        if let Some(rooms) = &build_data.rooms {
            for room in rooms.iter().skip(1) {
                spawner::spawn_room(&build_data.map, rng, room, build_data.map.depth, &mut build_data.spawn_list);
            }
        } else {
            panic!("Room Based Spawning only works after rooms have been created");
        }
    }