TableView member

Hi, the struct TableView, has among other members, items and rows_to_items:
pub struct TableView {
[...]
items: Vec,
rows_to_items: Vec,
[...]
}
The rows_to_items is in my opinion superfluous member and complicates code unnecessarily, as we can have all the information stored in the 'items'. What's the idea behind the rows_to_items member?
Thank you