private static object Factory(Type type, ImmutableJsonCoverterOptions options)
        {
            var ctor = typeof(ImmutableJsonConverter <>)
                       .MakeGenericType(type)
                       .GetConstructor(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance, null, new [] { typeof(ImmutableJsonCoverterOptions) }, null);

            return(ctor.Invoke(new object[] { options }));
        }
 public ImmutableJsonConverter(ImmutableJsonCoverterOptions options)
 => Options = options ?? ImmutableJsonCoverterOptions.Default;