Function labelled_records 

pub(crate) fn labelled_records(
    label_name: &'static str,
    value_name: &'static str,
    rows: &[(String, f64)],
) -> Records

A table of (label, value) rows, an absent label becoming an empty cell.

The unexplained leg of an attribution has no axis. It is carried as an empty label rather than dropped: a leg that vanished from the table would make the legs stop summing to the move they explain.