If lists are embedded in a page with other types of content, an inset list packages the list into a block that sits inside the content area with a bit of margin and rounded corners (theme controlled). Setting inset to True applies the inset appearance.
Note: all standard, non-inset lists have a -15 pixel margin to negate the 15 pixels of padding on the content area to make lists fill to the edges of the screen. If you add other content above or below a list, the negative margin may make these elements overlap so you'll need to add additional spacing in your custom CSS.
True, False, or any valid XPath expression that returns a boolean value.