Instead of
pub fn with_line_style(
inner: bool,
outer: bool,
cont: bool,
line_style: impl Into<LineStyle>,
) -> FrameCellDecorator {
we could have:
pub fn with_line_style(
inner: Option<impl Into<LineStyle>>,
outer: Option<impl Into<LineStyle>>,
cont: bool,
) -> FrameCellDecorator {