struct NatureThings: Decodable {
    let things: [NatureThing]

    init(from decoder: Decoder) throws {
        var container = try decoder.unkeyedContainer()
        var things: [NatureThing] = []
        while !container.isAtEnd {
            let superDecoder = try container.superDecoder()
            let typeContainer = try superDecoder.container(keyedBy: NatureThingTypeKey.self)
            guard let type = NatureThingType(rawValue: try typeContainer.decode(String.self, forKey: .type)) else {
                continue
            }

            switch type {
                case .mountain:
                    let mountain = try Mountain(from: superDecoder)
                    things.append(mountain)
                case .lake:
                    let lake = try Lake(from: superDecoder)
                    things.append(lake)
                case .cabin:
                    let cabin = try Cabin(from: superDecoder)
                    things.append(cabin)
            }
        }
        self.things = things
    }
}