Function list_items 

pub fn list_items(
    wb: &Workbook,
    sheet: usize,
    at: CellRef,
    dv: &Validation,
) -> Vec<String>

List entries of a list validation (literal or from a range) for the cell at. A relative source is written for the rule’s top-left cell and read from at, as in Excel (=$B1:$B3 on A1:A9 lists B5:B7 at A5).