public static Maybe <T> Collapse <T>(this Maybe <Maybe <T> > t) => t; // using implicit cast
/// <summary>
/// Flattens a recursive Maybe structure into IEnumerable
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="maybe"></param>
/// <param name="parentSelector"></param>
/// <example>
/// Having { a: 1, parent: { a: 2, parent: { a: 3, parent: Nothing } } }
/// We can flatten it to
/// [
/// { a: 1, parent: { a: 2, parent: { a: 3, parent: Nothing } } },
/// { a: 2, parent: { a: 3, parent: Nothing } } ,
/// { a: 3, parent: Nothing }
/// ]
/// </example>
/// <returns></returns>
public static IEnumerable <T> Flatten <T>(this Maybe <T> maybe, Func <T, Maybe <T> > parentSelector) =>
maybe.FlattenSelect(parentSelector, x => x);
