not conforming to protocol about baby HOT 1 OPEN

enum DecodingError: Error {
    case typeMismatch
}

enum MyData: Codable {
    case string(String)
    case double(Double)

    init(from decoder: Decoder) throws {
        let container = try decoder.singleValueContainer()
        if let x = try? container.decode(String.self) {
            self = .string(x)
            return
        }
        if let x = try? container.decode(Double.self) {
            self = .double(x)
            return
        }
        throw DecodingError.typeMismatch
    }

    func encode(to encoder: Encoder) throws {
        var container = encoder.singleValueContainer()
        switch self {
        case .string(let x):
            try container.encode(x)
        case .double(let x):
            try container.encode(x)
        }
    }
}

struct Aluminum: Codable {
    struct Dataset: Codable {
        let id: Int
        let datasetCode: String
        let databaseCode: String
        let name: String
        let description: String
        let refreshedAt: Date
        let newestAvailableDate: Date
        let oldestAvailableDate: Date
        let columnNames: [String]
        let frequency: String
        let type: String
        let premium: Bool
        let limit: Int?
        let transform: Int?
        let columnIndex: Int?
        let startDate: Date
        let endDate: Date
        let data: [[MyData]]
        let collapse: Int?
        let order: Int?
        let databaseId: Int
        private enum CodingKeys: String, CodingKey {
            case id
            case datasetCode = "dataset_code"
            case databaseCode = "database_code"
            case name
            case description
            case refreshedAt = "refreshed_at"
            case newestAvailableDate = "newest_available_date"
            case oldestAvailableDate = "oldest_available_date"
            case columnNames = "column_names"
            case frequency
            case type
            case premium
            case limit
            case transform
            case columnIndex = "column_index"
            case startDate = "start_date"
            case endDate = "end_date"
            case data
            case collapse
            case order
            case databaseId = "database_id"
        }
    }
    let dataset: Dataset
}