public static bool Possible(this Tristate v) => v != Tristate.No;
public static bool Impossible(this Tristate v) => v == Tristate.No;
public static bool IsMaybe(this Tristate v) => v == Tristate.Maybe;
public static bool IsNo(this Tristate v) => v == Tristate.No;
public static bool IsYes(this Tristate v) => v == Tristate.Yes;