Inheritance: RdioObject
        public RdioUserKeyStore(User user)
        {
            if (user == null)
                throw new ArgumentNullException (nameof (user));

            User = user;
        }
 public UserIsProtectedException(User user)
     : base(String.Format ("User is protected: {0}", user.DisplayName))
 {
     User = user;
 }