func background<Background>(Background, alignment: Alignment) -> Self.Modified<_BackgroundModifier<Background>> func background<S>(S.Member) -> Self.Modified<_BackgroundModifier<Rectangle.Filled<S>>> func background<S>(S.Member, cornerRadius: Length) -> Self.Modified<_BackgroundModifier<RoundedRectangle.Filled<S>>> func background<S>(S, cornerRadius: Length) -> Self.Modified<_BackgroundModifier<RoundedRectangle.Filled<S>>>