DictonaryExt.swift

extension Dictionary where Key : ExpressibleByStringLiteral {
    func extractValue<T>(key: String) throws -> T {
        let keyStr = key as! Key

        if let r = self[keyStr] as? T {
            return r
         } else {
            throw JSONDecodeError.missingValue(key: key, actualValue: self[keyStr])
        }
    }
}