public static async Task <T> Convert <T>(this IAsyncConvertible convertible, CancellationToken cancellationToken) => (T)await convertible.Convert(typeof(T), cancellationToken);
public static async Task <T> Convert <T>(this IAsyncConvertible convertible, T witness, CancellationToken cancellationToken) => await convertible.Convert <T>(cancellationToken);